Muscle derived cells for the treatment of cardiac pathologies and methods of making and using the same

ABSTRACT

The present invention provides muscle-derived progenitor cells that show long-term survival following transplantation into body tissues and which can augment soft tissue following introduction (e.g. via injection, transplantation, or implantation) into a site of soft tissue. Also provided are methods of isolating muscle-derived progenitor cells, and methods of genetically modifying the cells for gene transfer therapy. The invention further provides methods of using compositions comprising muscle-derived progenitor cells for the augmentation and bulking of mammalian, including human, soft tissues in the treatment of various cosmetic or functional conditions, including malformation, injury, weakness, disease, or dysfunction. In particular, the present invention provides treatments and amelioration for dermatological conditions, gastroesophageal reflux, vesico-ureteral reflux, urinary incontinence, fecal incontinence, heart failure, and myocardial infarction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser. No. 60/867,405, filed on Nov. 28, 2006, the disclosures of which are incorporated herein by reference in their entireties.

Each of the applications and patents cited in this text, as well as each document or reference cited in each of the applications and patents (including during the prosecution of each issued patent; “application cited documents”), and each of the U.S. and foreign applications or patents corresponding to and/or claiming priority from any of these applications and patents, and each of the documents cited or referenced in each of the application cited documents, are hereby expressly incorporated herein by reference. More generally, documents or references are cited in this text, either in a Reference List before the claims, or in the text itself; and, each of these documents or references (“herein-cited references”), as well as each document or reference cited in each of the herein-cited references (including any manufacturer's specifications, instructions, etc.), is hereby expressly incorporated herein by reference. Documents incorporated by reference into this text may be employed in the practice of the invention.

FIELD OF THE INVENTION

The present invention relates to muscle-derived progenitor cells (MDC) and compositions of MDCs and their use in the augmentation of body tissues, particularly soft tissue like cardiac muscle. In particular, the present invention relates to muscle-derived progenitor cells that show long-term survival following introduction into soft tissues and bone, methods of isolating MDCs, and methods of using MDC-containing compositions for the augmentation of human or animal soft tissues and bone, including epithelial, adipose, nerve, organ, muscle, ligament, and cartilage tissue. The invention also relates to novel uses of muscle-derived progenitor cells for the treatment of functional conditions, such as heart failure and injury or weakness associated with myocardial infarction.

BACKGROUND OF THE INVENTION

Augmentation of soft tissue using synthetic materials such as silicone or polytetrafluoroethylene (PTFE) is well known in the art. U.S. Pat. No. 5,876,447 to Arnett discloses the use of silicone implants for facial plastic surgery. However, such synthetic materials are foreign to the host tissue, and cause an immunological response resulting in the encapsulation of the implant and scarring of the surrounding tissues. Thus, the implant may produce additional functional or aesthetic problems.

Soft tissue augmentation using biopolymers such as collagen or hyaluronic acid has also been described. For example, U.S. Pat. No. 4,424,208 to Wallace et al. discloses methods of augmenting soft tissue utilizing collagen implant material. In addition, U.S. Pat. No. 4,965,353 to della Valle et al. discloses esters of hyaluronic acid that can be used in cosmetic surgery. However, these biopolymers are also foreign to the host tissue, and cause an immunological response resulting in the reabsorption of the injected material. Biopolymers are therefore unable to provide long-term tissue augmentation. Overall, the use of biopolymers or synthetic materials has been wholly unsatisfactory for the purpose of augmenting soft tissue.

Soft tissue augmentation using cell-based compositions has also been developed. U.S. Pat. No. 5,858,390 to Boss, Jr. discloses the use of autologous dermal fibroblasts for the treatment of cosmetic and aesthetic skin defects. Although this treatment avoids the problems inherent in the implantation or injection of synthetic materials or biopolymers, it results in other complications. Because fibroblasts produce collagen, the cells can cause the stiffening and distortion of the tissues surrounding the implant site.

The use of autologous fat cells as an injectable bulking agent has also been described (For review, see K. Mak et al., 1994, Otolaryngol. Clin. North. Am. 27:211 22; American Society of Plastic and Reconstructive Surgery: Report on autologous fat transplantation by the ad hoc committee on new procedures, 1987, Chicago: American Society of Plastic and Reconstructive Surgery; A. Chaichir et al., 1989, Plast. Reconstr. Surg. 84: 921 935; R. A. Ersek, 1991, Plast. Reconstr. Surg. 87:219 228; H. W. Horl et al., 1991, Ann. Plast. Surg. 26:248 258; A. Nguyen et al., 1990, Plast. Reconstr. Surg. 85:378 389; J. Bartynski et al., 1990, Otolaryngol. Head Neck Surg. 102:314 321. However, the fat grafting procedure provides only temporary augmentation, as injected fat is reabsorbed into the host. In addition, fat grafting can result in nodule formation and tissue asymmetry.

Myoblasts, the precursors of muscle fibers, are mononucleated muscle cells that fuse to form post-mitotic multinucleated myotubes, which can provide long-term expression and delivery of bioactive proteins (T. A. Partridge and K. E. Davies, 1995, Brit. Med. Bulletin 51:123 137; J. Dhawan et al., 1992, Science 254: 1509 12; A. D. Grinnell, 1994, Myology Ed 2, A. G. Engel and C. F. Armstrong, McGraw-Hill, Inc., 303 304; S. Jiao and J. A. Wolff, 1992, Brain Research 575:143 7; H. Vandenburgh, 1996, Human Gene Therapy 7:2195 2200).

Cultured myoblasts contain a subpopulation of cells that show some of the self-renewal properties of stem cells (A. Baroffio et al., 1996, Differentiation 60:47 57). Such cells fail to fuse to form myotubes, and do not divide unless cultured separately (A. Baroffio et al., supra). Studies of myoblast transplantation (see below) have shown that the majority of transplanted cells quickly die, while a minority survive and mediate new muscle formation (J. R. Beuchamp et al., 1999, J. Cell Biol. 144:1113 1122). This minority of cells shows distinctive behavior, including slow growth in tissue culture and rapid growth following transplantation, suggesting that these cells may represent myoblast stem cells (J. R. Beuchamp et al., supra).

Myoblasts have been used as vehicles for gene therapy in the treatment of various muscle- and non-muscle-related disorders. For example, transplantation of genetically modified or unmodified myoblasts has been used for the treatment of Duchenne muscular dystrophy (E. Gussoni et al., 1992, Nature, 356:435 8; J. Huard et al., 1992, Muscle & Nerve, 15:550 60; G. Karpati et al., 1993, Ann. Neurol., 34:8 17; J. P. Tremblay et al., 1993, Cell Transplantation, 2:99 112; P. A. Moisset et al., 1998, Biochem. Biophys. Res. Commun. 247:94 9; P. A. Moisset et al., 1998, Gene Ther. 5:1340 46). In addition, myoblasts have been genetically engineered-to produce proinsulin for the treatment of Type 1 diabetes (L. Gros et al., 1999, Hum. Gen. Ther. 10:1207 17); Factor IX for the treatment of hemophilia B (M. Roman et al., 1992, Somat. Cell. Mol. Genet. 18:247 58; S. N. Yao et al., 1994, Gen. Ther. 1:99 107; J. M. Wang et al., 1997, Blood 90:1075 82; G. Hortelano et al., 1999, Hum. Gene Ther. 10:1281 8); adenosine deaminase for the treatment of adenosine deaminase deficiency syndrome (C. M. Lynch et al., 1992, Proc. Natl. Acad. Sci. USA, 89:1138 42); erythropoietin for the treatment of chronic anemia (E. Regulier et al., 1998, Gene Ther. 5:1014 22; B. Dalle et al., 1999, Gene Ther. 6:157 61), and human growth hormone for the treatment of growth retardation (K. Anwer et al., 1998, Hum. Gen. Ther. 9:659 70).

Myoblasts have also been used to treat muscle tissue damage or disease, as disclosed in U.S. Pat. No. 5,130,141 to Law et al., U.S. Pat. No. 5,538,722 to Blau et al., and application U.S. Ser. No. 09/302,896 filed Apr. 30, 1999 by Chancellor et al. In addition, myoblast transplantation has been employed for the repair of myocardial dysfunction (C. E. Murry et al., 1996, J. Clin. Invest. 98:2512 23; B. Z. Atkins et al., 1999, Ann. Thorac. Surg. 67:124 129; B. Z. Atkins et al., 1999, J. Heart Lung Transplant. 18:1173 80).

In spite of the above, in most cases, primary myoblast-derived treatments have been associated with low survival rates of the cells following transplantation due to migration and/or phagocytosis. To circumvent this problem, U.S. Pat. No. 5,667,778 to Atala discloses the use of myoblasts suspended in a liquid polymer, such as alginate. The polymer solution acts as a matrix to prevent the myoblasts from migrating and/or undergoing phagocytosis after injection. However, the polymer solution presents the same problems as the biopolymers discussed above. Furthermore, the Atala patent is limited to uses of myoblasts in only muscle tissue, but no other tissue.

Thus, there is a need for other, different soft tissue augmentation materials that are long-lasting, compatible with a wide range of host tissues, and which cause minimal inflammation, scarring, and/or stiffening of the tissues surrounding the implant site. Accordingly, the muscle-derived progenitor cell-containing compositions of the present invention are provided as improved and novel materials for augmenting soft tissues. Further provided are methods of producing muscle-derived progenitor cell compositions that show long-term survival following transplantation, and methods of utilizing MDCs and compositions containing MDCs to treat various aesthetic and/or functional defects, including, for example, dermatological conditions or injury, and muscle weakness, injury, disease, or dysfunction.

It is notable that prior attempts to use myoblasts for non-muscle soft tissue augmentation were unsuccessful (U.S. Pat. No. 5,667,778 to Atala). Therefore, the findings disclosed herein are unexpected, as they show that the muscle-derived progenitor cells according to the present invention can be successfully transplanted into non-muscle and muscle soft tissue, including epithelial tissue, and exhibit long-term survival. As a result, MDCs and compositions comprising MDCs can be used as a general augmentation material for muscle or non-muscle soft tissue augmentation, as well as for bone production. Moreover, since the muscle-derived progenitor cells and compositions of the present invention can be derived from autologous sources, they carry a reduced risk of immunological complications in the host, including the reabsorption of augmentation materials, and the inflammation and/or scarring of the tissues surrounding the implant site.

Although mesenchymal stem cells can be found in various connective tissues of the body including muscle, bone, cartilage, etc. (H. E. Young et al., 1993, In Vitro Cell Dev. Biol. 29A:723 736; H. E. Young, et al., 1995, Dev. Dynam. 202:137 144), the term mesenchymal has been used historically to refer to a class of stem cells purified from bone marrow, and not from muscle. Thus, mesenchymal stem cells are distinguished from the muscle-derived progenitor cells of the present invention. Moreover, mesenchymal cells do not express the CD34 cell marker (M. F. Pittenger et al, 1999, Science 284:143 147), which is expressed by the muscle-derived progenitor cells described herein.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide novel muscle-derived progenitor cells (MDC) and MDC compositions exhibiting long-term survival following transplantation. The MDCs of this invention and compositions containing the MDCs comprise early progenitor muscle cells, i.e., muscle-derived stem cells, that express progenitor cell markers, such as desmin, M-cadherin, MyoD, myogenin, CD34, and Bcl-2. In addition, these early progenitor muscle cells express the Flk-1, Sca-1, MNF, and c-met cell markers, but do not express the CD45 or c-Kit cell markers.

It is another object of the present invention to provide methods for isolating and enriching muscle-derived progenitor cells from a starting muscle cell population. These methods result in the enrichment of MDCs that have long-term survivability after transplantation or introduction into a site of soft tissue. The MDC population according to the present invention is particularly enriched with cells that express progenitor cell markers, such as desmin, M-cadherin, MyoD, myogenin, CD34, and Bcl-2. This MDC population also expresses the Flk-1, Sca-1, MNF, and c-met cell markers, but does not express the CD45 or c-Kit cell markers.

It is yet another object of the present invention to provide methods of using MDCs and compositions comprising MDCs for the augmentation of muscle soft tissue, or non-muscle soft tissue, including skin, blood vessels, adipose, nerve, skeletal muscle, smooth muscle, ligament, cartilage, and various organ tissues, without the need for polymer carriers or special culture media for transplantation. Such methods include the administration of MDC compositions by introduction into soft tissue, for example by direct injection into tissue, or by systemic distribution of the compositions. Preferably, soft tissue includes non-bone body tissues. More preferably, soft tissue includes non-striated muscle, non-bone body tissues. Most preferably, soft tissue includes non-muscle, non-bone body tissues. As used herein, augmentation refers to filling, bulking, supporting, enlarging, extending, or increasing the size or mass of body tissue.

It is another object of the present invention to provide MDC-based treatments for a) cosmetic or aesthetic conditions; b) gastroesophageal reflux symptoms and conditions; c) fecal and urinary incontinence; d) skeletal and smooth muscle weakness, injury, disease, or dysfunction and e) cardiac conditions including myocardial infarction.

It is yet another object of the present invention to provide methods of augmenting bone or soft tissue, either muscle-derived soft tissue, or non-muscle-derived soft tissue, following injury, wounding, surgeries, traumas, non-traumas, or other procedures that result in fissures, openings, depressions, wounds, and the like, in the skin or in internal soft tissues or organs.

It is a further object of the present invention to provide MDCs and compositions comprising MDCs that are modified through the use of chemicals, growth media, and/or genetic manipulation. Such MDCs and compositions thereof comprise chemically or genetically modified cells useful for the production and delivery of biological compounds, and the treatment of various diseases, conditions, injuries, or illnesses.

It is yet another embodiment of the invention to provide pharmaceutical compositions comprising MDCs and compositions comprising MDCs. These pharmaceutical compositions comprise isolated MDCs. These MDCs may be subsequently expanded by cell culture after isolation. These MDCs are frozen prior to delivery to a subject in need of the pharmaceutical composition.

In one embodiment, when the MDCs and compositions thereof are used to treat cardiac conditions, they are injected directly into the heart. They may be injected into the chambers of the heart or into the heart wall.

The invention also provides compositions and methods involving the isolation of MDCs using a single plating technique. MDCs are isolated from a biopsy of skeletal muscle. In one embodiment, the skeletal muscle from the biopsy may be stored for 1-30 days. In one aspect of this embodiment, the skeletal muscle from the biopsy is stored at 4° C. In another aspect of this embodiment, the skeletal muscle from the biopsy is stored at 10° C. The cells are minced, and digested using a collagenase, dispase, another enzyme or a combination of enzymes. After washing the enzyme from the cells, the cells are cultured in a flask in culture medium for between about 30 and about 120 minutes. During this period of time, the “rapidly adhering cells” stick to the walls of the flask or container, while the “slowly adhering cells” or MDCs remain in suspension. The “slowly adhering cells” are transferred to a second flask or container and cultured therein for a period of 1-3 days. During this second period of time the “slowly adhering cells” or MDCs stick to the walls of the second flask or container.

In another embodiment of the invention, these MDCs are expanded to any number of cells. In a preferred aspect of this embodiment, the cells are expanded in new culture media for between about 10 and 20 days. More preferably, the cells are expanded for 17 days.

The MDCs, whether expanded or not expanded, may be preserved in order to be transported or stored for a period of time before use. In one embodiment, the MDCs are frozen. Preferably, the MDCs are frozen at between about −20 and −90° C. More preferably, the MDCs are frozen at about −80° C. These frozen MDCs are used as a pharmaceutical composition.

MDCs, whether frozen or preserved as a pharmaceutical composition, or used fresh, may be used to treat a number of cardiac conditions. These conditions include myocardial infarction, heart failure, Adams-Stokes disease, congenital heart disease, angina pectoris, arrhythmias, atrial fibrillation, bacterial endocarditis, cardiomyopathy, congestive heart failure, diastolic dysfunction, heart murmurs, and premature ventricular contractions. The MDCs may be used to cure heart defects caused by any cardiac pathology or to improve cardiac function. In one embodiment, MDCs are administered directly to the heart.

Preferably, MDCs are used to treat myocardial infarction (MI). In one embodiment, this treatment is performed by isolating MDCs from skeletal muscle collected from a MI patient, and administering the patient's own MDCs back to the patient's heart. This treatment increases function of the patient's heart and deleterious heart remodeling and scarring that occurs after MI.

Additional objects and advantages afforded by the present invention will be apparent from the detailed description and exemplification hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings of the figures are presented to further describe the invention and to assist in its understanding through clarification of its various aspects.

FIGS. 1A-1F illustrate the results of soft tissue augmentation utilizing injections of MDC compositions compared with injection of conventional bovine collagen. For FIGS. 1A-1F, either MDCs (FIGS. 1D-1F) or collagen (1A-1C) were injected into the skin of the abdominal wall. The area of injection was the interface of the dermis and the subcutaneous connective tissue which is the skin. FIGS. 1A 1F show Trichrome staining at 40× magnification following injection of either collagen or MDCs into skin. At 5 days, 2 weeks, or 4 weeks post-injection, tissue samples were obtained and prepared for analysis. FIGS. 1A and 1D show the results of MDCs versus collagen injection into the skin at 5 days post-injection; FIGS. 1B and 1E show the results at 2 weeks post-injection; and FIGS. 1C and 1F show the results at 4 weeks post-injection. Arrowheads in FIGS. 1D-1F indicate the presence of MDCs in the injected areas (deep pink color). FIGS. 1A-1F demonstrate that following injection into the subcutaneous space, MDCs persisted and maintained/augmented the abdominal wall subcutaneous tissue for up to at least 4 weeks, while collagen did not persist by 2 weeks post-injection into the skin. (Example 3).

FIGS. 2A and 2B illustrate the results of lower esophageal (FIG. 2A) and anal sphincter (FIG. 2B) soft tissue augmentation utilizing injections of MDCs compositions. Injections were made into the gastroesophageal junction or anal sphincter. At day 3 post-injection, tissue samples were obtained and prepared for analysis. MDCs are indicated by β-galactosidase staining. FIG. 2A shows injected tissues at 100× magnification; FIG. 2B shows injected tissues at 40× magnification. FIGS. 2A and 2B demonstrates that MDC injections maintained the lower esophageal sphincter and anal sphincter soft tissue augmentation for up to 3 days following injection

FIGS. 3A and 3B illustrate the results of bladder-ureteral junction soft tissue augmentation utilizing injections of MDCs compositions. Injections were made into the vesico-ureteral junction. At day 3 post-injection, tissue samples were obtained and prepared for analysis. MDCs are indicated by β-galactosidase staining as viewed near the arrow. FIG. 3A shows injected tissues at low (40×) magnification; FIG. 3B shows injected tissues at high (100×) magnification. FIGS. 3A and 3B demonstrate that MDC injections maintained the bladder-ureteral junction soft tissue augmentation for up to 3 days following injection

FIGS. 4A and 4B illustrate the treatment of bladder cryoinjury utilizing soft tissue injections of MDCs compositions. Injections were made into the bladder wall at the site of cryoinjury. At day 30 post-injection, tissue samples were obtained and prepared for staining. Arrows indicate site of cryoinjury and MDC injection. Magnification is 100×. FIG. 4A shows untreated cryodamaged bladder tissue. FIG. 4B shows cryodamaged bladder tissue treated with MDC injections; MDCs are indicated by β-galactosidase staining. FIGS. 4A and 4B demonstrate that MDC injections maintained the soft tissue augmentation of the cryodamaged bladder tissue for up to 30 days following injection.

FIGS. 5A-5I illustrate cellular differentiation of MDCs following injection into cryodamaged bladder tissue. Injections were made into the bladder wall at the site of cryoinjury, and tissue samples were obtained and prepared for analysis at 5, 35, or 70 days post-injection. Injected MDCs are shown by staining for α-galactosidase, and undifferentiated MDCs are shown by α-smooth muscle actin (α-SM actin) staining. MDCs that have differentiated into myotubes or myofibers are shown by fast myosin heavy chain (fast MyHC) staining. Arrows show fast MyHC. At day 5 post-injection, multiple MDCs are observed at the injection area and only some MDCs have differentiated into myotubes, as shown by the high levels of β-galactosidase (FIG. 5A) and α-SM actin (FIG. 5D) staining, and the relatively low levels of Fast MyHC (FIG. 5G) staining. At day 35 post-injection, multiple MDCs are observed at the injection area, and many have differentiated into myotubes, as shown by the high levels of β-galactosidase staining (FIG. 5B), the decrease in α-SM actin (FIG. 5E) staining; and the increase in Fast MyHC (FIG. 5H) staining. At day 70 post-injection, MDCs are observed at the injection area, and almost all MDCs have differentiated into myofibers, as shown by the high levels of β-galactosidase (FIG. 5C), the decrease in α-SM actin (FIG. 5F) staining, and the high levels of Fast MyHC (FIG. 5I) staining. Magnification is 200×. FIGS. 5A-5I demonstrate that MDCs remain viable and begin differentiation for up to 70 days following injection into bladder soft tissue.

FIGS. 6A-6D illustrate the reinnervation of MDC injected into the soft tissue of the urinary bladder. Innervation is indicated by acetylcholine (Ach) staining, which shows the neuromuscular junction. At day 3 post-injection, few innervations are observed, as shown by Ach staining (FIG. 6A). At day 15 post injection, several innervations are observed (FIG. 6B). At day 30 post-injection, more innervations are observed (FIG. 6C). After 6 months post-injection, numerous innervations are observed at low (100×) magnification (FIG. 6D). FIGS. 6A-6C show injected tissue at high (200×) magnification. FIGS. 6A-6D demonstrate that MDCs induce innervation for up to 6 months following injection into cryodamaged bladder tissues.

FIGS. 7A and 7B illustrate the results of soft tissue augmentation of myocardial smooth muscle utilizing injections of MDCs compositions. Injections were made into the ventricular wall, and tissue samples were prepared 3 days post-injection. MDCs are indicated by β-galactosidase staining. FIG. 7A shows injected tissue at low (100×) magnification; FIG. 7B shows injected tissue at high (200×) magnification.

FIGS. 8A and 8B illustrate the results of MDC injections into liver tissue. Injections were made into liver tissue in the lower left lobe, and tissue samples were prepared 4 days post-injection. MDCs are indicated by β-galactosidase staining. FIG. 8A shows low (100×) magnification; FIG. 8B shows high (200×) magnification.

FIGS. 9A and 9B illustrate the results of MDC injections into spleen tissue. Injections were made into spleen tissue in the interior aspect, and tissue samples were prepared 4 days post-injection. MDCs are indicated by β-galactosidase staining. FIG. 9A shows injected tissues viewed by low (100×) magnification; FIG. 9B shows injected tissues viewed by high (200×) magnification.

FIGS. 10A and 10B illustrate the results of MDC injections into spinal cord tissue. Injections were made into spinal cord tissue, and tissue samples were prepared 4 days post-injection. MDCs are indicated by β-galactosidase staining. FIG. 10A shows injected tissues viewed by low (100×) magnification; FIG. 10B shows injected tissues viewed by high (200×) magnification. FIGS. 7A-7B, 8A-8B, 9A-9B, and 10A-10B demonstrate that MDCs remain viable following injection into a variety of different tissue types without damaging the host tissues.

FIGS. 11A-11L illustrate immunohistochemical analysis of PP1-4 and PP6 cell populations from mdx mice showing expression of cell markers including desmin, MyoD, and myogenin (markers specific for myogenic lineages), M-cadherin (satellite cell specific marker), Bcl-2 (early myogenesis marker), CD34 (hematopoietic or stromal cell marker). FIGS. 11A-11L demonstrate that PP14 and PP6 cell populations show comparable percentage of cells expressing desmin (FIGS. 11A and 11G), MyoD (FIGS. 11E and 11K), and myogenin (FIGS. 11F and 11L), while the PP6 population shows a lower percentage of cells expressing M-cadherin (FIGS. 11D and 11J), but a higher percentage of cells expressing Bcl-2 (FIGS. 11C and 11I) and CD34 (FIGS. 11B and 11H), compared with the PP1-4 population.

FIGS. 12A-12I illustrate the intracellular co-localization of CD34 or Bcl-2 staining with desmin staining in mouse muscle cells and vascular endothelial cells. FIG. 12A shows normal mouse muscle cells (see arrow) and vascular endothelial cells (see arrowhead) stained with anti-CD34 antibodies and visualized by fluorescence microscopy. FIG. 12B shows the same cells co-stained with desmin and collagen type IV antibodies. FIG. 12C shows the same cells co-stained with Hoechst to show the nuclei. FIG. 12D shows a composite of the cells co-stained for CD34, desmin, collagen type IV, and Hoechst. FIG. 12E shows normal mouse muscle cells (see arrow) stained with anti-Bcl-2 antibodies and visualized by fluorescence microscopy. FIG. 12F shows the same cells co-stained with desmin and collagen type IV antibodies. FIG. 12G shows the same cells co-stained with Hoechst to show the nuclei. FIG. 12H shows a composite of the cells co-stained for CD34, desmin, collagen type IV, and Hoechst. FIG. 12I shows satellite cells stained with anti-M-cadherin antibodies (see arrow). Cells were viewed at 40× magnification. FIGS. 12A-12D demonstrate the co-localization of CD34 and desmin, while FIGS. 12E-12H demonstrate the co-localization of Bcl-2 and desmin.

FIGS. 13A-E illustrate the morphologic changes and expression of osteocalcin resulting from the exposure of mc13 cells to rhBMP-2. Mc13 cells were incubated in growth media with or without rhBMP-2 for 6 days. FIG. 13A shows cells grown to >50% cell confluency in the absence of rhBMP-2. FIG. 13B shows cells grown to >50% cell confluency in the presence of 200 ng/ml rhBMP-2. FIG. 13C shows cells grown to >90% cell confluency in the absence of rhBMP-2. FIG. 13D shows cells grown to >90% confluency in the presence of 200 ng/ml rhBMP-2. FIG. 13E shows cells stained for osteocalcin expression (osteoblast cell marker; see arrows). Cells were viewed at 10× magnification. FIGS. 13A-13E demonstrate that mc13 cells are capable of differentiating into osteoblasts upon exposure to rhBMP-2.

FIGS. 14A-14D illustrate the effects on the percentage of mc13 cells expressing desmin and alkaline phosphatase in response to rhBMP-2 treatment. FIG. 14A shows desmin staining of newly isolated mc13 clones. FIG. 14B shows a phase contrast view of the same cells. FIG. 14C shows the levels of desmin staining in mc13 cells following 6 days of incubation in growth media with or without 200 ng/ml rhBMP-2. FIG. 14D shows the levels of alkaline phosphate staining in PP1 4 cells and mc13 cells following 6 days of incubation in growth media with or without 200 ng/ml rhBMP-2. *indicates a statistically significant result (student's t-test). FIG. 14C demonstrates that a decreasing number of mc13 cells express desmin in the presence of rhBMP-2, while FIG. 14D demonstrates that an increasing number of mc13 cells express alkaline phosphatase in the presence of rhBMP-2, suggesting decreasing myogenic characteristics and increasing osteogenic characteristics of the cells in the presence of rhBMP-2.

FIGS. 15A-15G illustrate the in vivo differentiation of mc13 cells into myogenic and osteogenic lineages. Mc13 cells were stably transfected with a construct containing LacZ and the dystrophin gene, and introduced by intramuscular or intravenous injection into hind limbs of mdx mice. After 15 days, the animals were sacrificed and the hind limb musculature was isolated for histology. FIG. 15A shows mc13 cells at the intramuscular injection site stained for LacZ. FIG. 15B shows the same cells co-stained for dystrophin. FIG. 15C shows mc13 cells in the region of the intravenous injection stained for LacZ. FIG. 15D shows the same cells co-stained for dystrophin. In a separate experiment, mc13 cells were transduced with adBMP-2, and 0.5 1.0×10⁶ cells were injected into hind limbs of SCID mice. After 14 days, the animals were sacrificed, and the hind limb muscle tissues were analyzed. FIG. 15E shows radiographic analysis of the hind limb to determine bone formation. FIG. 15F shows the cells derived from the hind limb stained for LacZ. FIG. 15G shows cells stained for dystrophin. FIGS. 15A 15D demonstrate that mc13 cells can rescue dystrophin expression via intramuscular or intravenous delivery. FIGS. 15E-15G demonstrate that mc13 cells are involved in ectopic bone formation. Cells were viewed at the following magnifications: 40× (FIGS. 15A-15D), 10× (FIGS. 15F-15G)

FIGS. 16A-16E illustrate the enhancement of bone healing by rhBMP-2 producing primary muscle cells. A 5 mm skull defect was created in female SCID mice using a dental burr, and the defect was filled with a collagen sponge seeded with mc13 cells with or without adBMP-2. The animals were sacrificed at 14 days, inspected, and analyzed microscopically for indications of bone healing. FIG. 16A shows a skull treated with mc13 cells without adBMP-2. FIG. 16B shows a skull treated with mc13 cells transduced with adBMP-2. FIG. 16C shows a histological sample of the skull treated with mc13 cells without adBMP-2 analyzed by von Kossa staining. FIG. 16D shows a histological sample of the skull treated with mc13 cells transduced with adBMP-2 analyzed by von Kossa staining. FIG. 16E shows a histological sample of the skull treated with the mc13 cells transduced with adBMP-2 analyzed by hybridization with a Y-chromosome specific probe to identify the injected cells (green fluorescence shown by arrows), and stained with ethidium bromide to identify the nuclei (indicated by red fluorescence). FIGS. 16A 16E demonstrate that mc13 cells expressing rhBMP-2 can contribute to the healing of bone defects.

FIGS. 17A and 17B are graphs showing the amount of creatine kinase activity at various % expression of CD56 for rapidly adhering and slowly adhering cells respectively.

FIG. 18 is a series of bar graphs showing the fractional area change (FAC) an index of left ventricular contractility in control cells and rapidly adhering and slowly adhering MDCs at 2 weeks and 6 weeks after intracardial injection.

DETAILED DESCRIPTION OF THE INVENTION

Muscle-Derived Cells and Compositions

The present invention provides MDCs comprised of early progenitor cells (also termed muscle-derived progenitor cells or muscle-derived stem cells herein) that show long-term survival rates following transplantation into body tissues, preferably soft tissues. To obtain the MDCs of this invention, a muscle explant, preferably skeletal muscle, is obtained from an animal donor, preferably from a mammal, including humans. This explant serves as a structural and functional syncytium including “rests” of muscle precursor cells (T. A. Partridge et al., 1978, Nature 73:306 8; B. H. Lipton et al., 1979, Science 205:12924).

Cells isolated from primary muscle tissue contain mixture of fibroblasts, myoblasts, adipocytes, hematopoietic, and muscle-derived progenitor cells. The progenitor cells of a muscle-derived population can be enriched using differential adherence characteristics of primary muscle cells on collagen coated tissue flasks, such as described in U.S. Pat. No. 6,866,842 of Chancellor et al. Cells that are slow to adhere tend to be morphologically round, express high levels of desmin, and have the ability to fuse and differentiate into multinucleated myotubes U.S. Pat. No. 6,866,842 of Chancellor et al.). A subpopulation of these cells was shown to respond to recombinant human bone morphogenic protein 2 (rhBMP-2) in vitro by expressing increased levels of alkaline phosphatase, parathyroid hormone dependent 3′,5′-cAMP, and osteogenic lineage and myogenic lineages (U.S. Pat. No. 6,866,842 of Chancellor et al.; T. Katagiri et al., 1994, J. Cell Biol., 127:1755 1766).

In one embodiment of the invention, a preplating procedure may be used to differentiate rapidly adhering cells from slowly adhering cells (MDCs). In accordance with the present invention, populations of rapidly adhering cells (PP1 4) and slowly adhering, round MDCs (PP6) were isolated and enriched from skeletal muscle explants and tested for the expression of various markers using immunohistochemistry to determine the presence of pluripotent cells among the slowly adhering cells (Example 1; patent application U.S. Ser. No. 09/302,896 of Chancellor et al.). As shown in Table 3, Example 9 herein, the PP6 cells expressed myogenic markers, including desmin, MyoD, and Myogenin. The PP6 cells also expressed c-met and MNF, two genes which are expressed at an early stage of myogenesis (J. B. Miller et al., 1999, Curr. Top. Dev. Biol. 43:191 219; see Table 3). The PP6 showed a lower percentage of cells expressing M-cadherin, a satellite cell-specific marker (A. Irintchev et al., 1994, Development Dynamics 199:326 337), but a higher percentage of cells expressing Bcl-2, a marker limited to cells in the early stages of myogenesis (J. A. Dominov et al., 1998, J. Cell Biol. 142:537 544). The PP6 cells also expressed CD34, a marker identified with human hematopoietic progenitor cells, as well as stromal cell precursors in bone marrow (R. G. Andrews et al., 1986, Blood 67:842 845; C. I. Civin et al., 1984, J. Immunol. 133:157 165; L. Fina et al, 1990, Blood 75:2417 2426; P. J. Simmons et al., 1991, Blood 78:2848 2853; see Table 3). The PP6 cells also expressed Flk-1, a mouse homologue of human KDR gene which was recently identified as a marker of hematopoietic cells with stem cell-like characteristics (B. L. Ziegler et al., 1999, Science 285:1553 1558; see Table 3). Similarly, the PP6 cells expressed Sca-1, a marker present in hematopoietic cells with stem cell-like characteristics (M. van de Rijn et al., 1989, Proc. Natl. Acad. Sci. USA 86:4634 8; M. Osawa et al., 1996, J. Immunol. 156:3207 14; see Table 3). However, the PP6 cells did not express the CD45 or c-Kit hematopoietic stem cell markers (reviewed in L K. Ashman, 1999, Int. J. Biochem. Cell. Biol. 31:1037 51; G. A. Koretzky, 1993, FASEB J. 7:420 426; see Table 3).

In one embodiment of the present invention is the PP6 population of muscle-derived progenitor cells having the characteristics described herein. These muscle-derived progenitor cells express the desmin, CD34, and Bcl-2 cell markers. In accordance with the present invention, the PP6 cells are isolated by the techniques described herein (Example 1) to obtain a population of muscle-derived progenitor cells that have long-term survivability following transplantation. The PP6 muscle-derived progenitor cell population comprises a significant percentage of cells that express progenitor cell markers such as desmin, CD34, and Bcl-2. In addition, PP6 cells express the Flk-1 and Sca-1 cell markers, but do not express the CD45 or c-Kit markers. Preferably, greater than 95% of the PP6 cells express the desmin, Sca-1, and Flk-1 markers, but do not express the CD45 or c-Kit markers. It is preferred that the PP6 cells are utilized within about 1 day or about 24 hours after the last plating.

In a preferred embodiment, the rapidly adhering cells and slowly adhering cells (MDCs) are separated from each other using a single plating technique. One such technique is described in Example 10. First, cells are provided from a skeletal muscle biopsy. The biopsy need only contain about 100 mg of cells. Biopsies ranging in size from about 50 mg to about 500 mg are used according to both the pre-plating and single plating methods of the invention. Further biopsies of 50, 100, 110, 120, 130, 140, 150, 200, 250, 300, 400 and 500 mg are used according to both the pre-plating and single plating methods of the invention. In one embodiment, the tissue from biopsy is processed within 24 hours after it is procured.

In a preferred embodiment of the invention, the tissue from the biopsy is then stored for 1 to 30 days. This storage is at a temperature from about room temperature to about 4° C. This waiting period causes the biopsied skeletal muscle tissue to undergo stress. While this stress is not necessary for the isolation of MDCs using this single plate technique, it seems that using the wait period results in a greater yield of MDCs.

Tissue from the biopsies is minced and centrifuged. The pellet is resuspended and digested using a digestion enzyme. Enzymes that me be used include collagenase, dispase or combinations of these enzymes. After digestion, the enzyme is washed off of the cells. The cells are transferred to a flask in culture media for the isolation of the rapidly adhering cells. Many culture media may be used. Particularly preferred culture media include those that are designed for culture of endothelial cells including Cambrex Endothelial Growth Medium. This medium may be supplemented with other components including fetal bovine serum, IGF-1, bFGF, VEGF, EGF, hydrocortisone, heparin, and/or ascorbic acid. Other media that may be used in the single plating technique include InCell M310F medium. This medium may be supplemented as described above, or used unsupplemented.

The step for isolation of the rapidly adhering cells may require culture in flask for a period of time from about 30 to about 120 minutes. The rapidly adhering cells adhere to the flask in 30, 40, 50, 60, 70, 80, 90, 100, 110 or 120 minutes. After they adhere, the slowly adhering cells are separated from the rapidly adhering cells from removing the culture media from the flask to which the rapidly adhering cells are attached to. In certain embodiments the slowly adhering cells (MDCs) are cooled to a temperature lower than 10° C. after they are isolated.

The culture medium removed from this flask is then transferred to a second flask. The cells may be centrifuged and resuspended in culture medium before being transferred to the second flask. The cells are cultured in this second flask for between 1 and 3 days. Preferably, the cells are cultured for two days. During this period of time, the slowly adhering cells (MDCs) adhere to the flask. After the MDCs have adhered, the culture media is removed and new culture media is added so that the MDCs can be expanded in number. The MDCs may be expanded in number by culturing them for from about 10 to about 20 days. The MDCs may be expanded in number by culturing them for 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 days. Preferably, the MDCs are subject to expansion culture for 17 days.

As an alternative to the pre-plating and single plating methods, the MDCs of the present invention can be isolated by fluorescence-activated cell sorting (FACS) analysis using labeled antibodies against one or more of the cell surface markers expressed by the MDCs (C. Webster et al., 1988, Exp. Cell. Res. 174:252 65; J. R. Blanton et al., 1999, Muscle Nerve 22:43 50). For example, FACS analysis can be performed using labeled antibodies to directed to CD34, Flk-1, Sca-1, and/or the other cell-surface markers described herein to select a population of PP6-like cells that exhibit long-term survivability when introduced into the host tissue. Also encompassed by the present invention is the use of one or more fluorescence-detection labels, for example, fluorescein or rhodamine, for antibody detection of different cell marker proteins.

Using any of the MDCs isolation methods described above, MDCs that are to be transported, or are not going to be used for a period of time may be preserved using methods known in the art. More specifically, the isolated MDCs may be frozen to a temperature ranging from about −25 to about −90° C. Preferably, the MDCs are frozen at about −80° C., on dry ice for delayed use or transport. The freezing may be done with any cryopreservation medium known in the art.

Muscle-Derived Cell-Based Treatments

In one embodiment of the present invention, the MDCs are isolated from a skeletal muscle source and introduced or transplanted into a muscle or non-muscle soft tissue site of interest, or into bone structures. Advantageously, the MDCs of the present invention are isolated and enriched to contain a large number of progenitor cells showing long-term survival following transplantation. In addition, the muscle-derived progenitor cells of this invention express a number of characteristic cell markers, such desmin, CD34, and Bcl-2. Furthermore, the muscle-derived progenitor cells of this invention express the Sca-1, and Flk-1 cell markers, but do not express the CD45 or c-Kit cell markers (see Example 1).

MDCs and compositions comprising MDCs of the present invention can be used to repair, treat, or ameliorate various aesthetic or functional conditions (e.g. defects) through the augmentation of muscle or non-muscle soft tissues. In particular, such compositions can be used as soft-tissue bulking agents for the treatment of: 1) cosmetic and aesthetic conditions of the skin; 2) conditions of the lumen; 3) gastroesophageal reflux symptoms or conditions; 4) fecal incontinence; 5) skeletal muscle weakness, disease, injury or dysfunction; and 6) smooth muscle weakness, disease, injury, or dysfunction. In addition, such MDCs and compositions thereof can be used for augmenting soft tissue not associated with injury by adding bulk to a soft tissue area, opening, depression, or void in the absence of disease or trauma, such as for “smoothing” or removing a wrinkle. Multiple and successive administrations of MDCs are also embraced by the present invention.

For MDC-based treatments, a skeletal muscle explant is preferably obtained from an autologous or heterologous human or animal source. An autologous animal or human source is more preferred. MDC compositions are then prepared and isolated as described herein. To introduce or transplant the MDCs and/or compositions comprising the MDCs according to the present invention into a human or animal recipient, a suspension of mononucleated muscle cells is prepared. Such suspensions contain concentrations of the muscle-derived progenitor cells of the invention in a physiologically-acceptable carrier, excipient, or diluent. For example, suspensions of MDCs for administering to a subject can comprise 10⁸ to 10⁹ cells/ml in a sterile solution of complete medium modified to contain the subject's serum, as an alternative to fetal bovine serum. Alternatively, MDC suspensions can be in serum-free, sterile solutions, such as cryopreservation solutions (Celox Laboratories, St. Paul, Minn.). The MDC suspensions can then be introduced e.g., via injection, into one or more sites of the donor tissue.

The described cells can be administered as a pharmaceutically or physiologically acceptable preparation or composition containing a physiologically acceptable carrier, excipient, or diluent, and administered to the tissues of the recipient organism of interest, including humans and non-human animals. The MDC-containing composition can be prepared by resuspending the cells in a suitable liquid or solution such as sterile physiological saline or other physiologically acceptable injectable aqueous liquids. The amounts of the components to be used in such compositions can be routinely determined by those having skill in the art.

The MDCs or compositions thereof can be administered by placement of the MDC suspensions onto absorbent or adherent material, i.e., a collagen sponge matrix, and insertion of the MDC-containing material into or onto the site of interest. Alternatively, the MDCs can be administered by parenteral routes of injection, including subcutaneous, intravenous, intramuscular, and intrasternal. Other modes of administration include, but are not limited to, intranasal, intrathecal, intracutaneous, percutaneous, enteral, and sublingual. In one embodiment of the present invention, administration of the MDCs can be mediated by endoscopic surgery.

For injectable administration, the composition is in sterile solution or suspension or can be resuspended in pharmaceutically- and physiologically-acceptable aqueous or oleaginous vehicles, which may contain preservatives, stabilizers, and material for rendering the solution or suspension isotonic with body fluids (i.e. blood) of the recipient. Non-limiting examples of excipients suitable for use include water, phosphate buffered saline, pH 7.4, 0.15 M aqueous sodium chloride solution, dextrose, glycerol, dilute ethanol, and the like, and mixtures thereof. Illustrative stabilizers are polyethylene glycol, proteins, saccharides, amino acids, inorganic acids, and organic acids, which may be used either on their own or as admixtures. The amounts or quantities, as well as the routes of administration used, are determined on an individual basis, and correspond to the amounts used in similar types of applications or indications known to those of skill in the art.

To optimize transplant success, the closest possible immunological match between donor and recipient is desired. If an autologous source is not available, donor and recipient Class I and Class II histocompatibility antigens can be analyzed to determine the closest match available. This minimizes or eliminates immune rejection and reduces the need for immunosuppressive or immunomodulatory therapy. If required, immunosuppressive or immunomodulatory therapy can be started before, during, and/or after the transplant procedure. For example, cyclosporin A or other immunosuppressive drugs can be administered to the transplant recipient. Immunological tolerance may also be induced prior to transplantation by alternative methods known in the art (D. J. Watt et al., 1984, Clin. Exp. Immunol. 55:419; D. Faustman et al., 1991, Science 252:1701).

Consistent with the present invention, the MDCs can be administered to body tissues, including bone, epithelial tissue (i.e., skin, lumen, etc.), connective tissue (i.e., adipose, cartilage, ligament, lymph, etc.), muscle tissue (i.e., skeletal/striated or smooth muscle), and various organ tissues such as those organs that are associated with the digestive system (i.e., mouth, tongue, esophagus, stomach, liver, pancreas, gall bladder, intestine, anus, etc.), cardiovascular system (i.e., heart, veins, arteries, capillaries, etc.), respiratory system (i.e., lungs, trachea, etc.), reproductive system (i.e., vas deferens, scrotum, testes, penis, fallopian tubes, vagina, clitoris, uterus, breasts, ovaries, vulva, etc.), urological system (i.e., bladder, urethra, ureter, kidneys, etc.), and nervous system (i.e., brain, spinal cord, nerves, etc.).

The number of cells in an MDC suspension and the mode of administration may vary depending on the site and condition being treated. As non-limiting examples, in accordance with the present invention, about 1−1.5×10⁶ MDCs are injected for the treatment of an approximately 8 mm diameter region of cryodamage in bladder smooth muscle tissue (see Example 6), while about 0.5−1.0×10⁶ MDCs are administered via a collagen sponge matrix for the treatment of an approximately 5 mm region of skull defect (see Example 9). Consistent with the Examples disclosed herein, a skilled practitioner can modulate the amounts and methods of MDC-based treatments according to requirements, limitations, and/or optimizations determined for each case.

Dermatological conditions: The MDCs and compositions thereof according to the present invention have marked utility as materials for soft tissue augmentation in cosmetic procedures, e.g., plastic surgery or anti-aging procedures. Specifically, such MDCs and MDC-containing compositions can be used to treat various dermatological conditions in a human or animal subject, including, but not limited to, wounds, wrinkles, rhytids, cutaneous depressions of non-traumatic origin, stretch marks, depressed scars, scaring from acne vulgaris, and hypoplasia of the lip. More specifically, the MDCs and compositions of the present invention can be used to treat wrinkles, rhytids, or cutaneous depressions of the face, and especially, the region surrounding the eye(s). To treat dermatological conditions, the MDCs are prepared as disclosed herein and then administered, e.g. via injection, to the skin, subcutaneously or intradermally, to fill, bulk up, or repair the defect. The number of MDCs introduced is modulated to repair deep cutaneous depressions or defects, as well as superficial surface depressions or defects, as required. For example, about 1 1.5×10⁶ MDCs are utilized for the augmentation of an approximately 5 mm region of the skin (see Example 3).

Conditions of the lumen: In another embodiment, the MDCs and compositions thereof according to the present invention have further utility as treatments for conditions of the lumen in an animal or mammal subject, including humans. Specifically, the muscle-derived progenitor cells are used for completely or partially blocking, enhancing, enlarging, sealing, repairing, bulking, or filling various biological lumens or voids within the body. Lumens include, without limitation, blood vessels, intestine, stomach, esophagus, urethra, vagina, Fallopian tubes, vas deferens, and trachea. Voids may include, without limitation, various tissue wounds (i.e., loss of muscle and soft tissue bulk due to trauma; destruction of soft tissue due to penetrating projectiles such as a stab wound or bullet wound; loss of soft tissue from disease or tissue death due to surgical removal of the tissue including loss of breast tissue following a mastectomy for breast cancer or loss of muscle tissue following surgery to treat sarcoma, etc.), lesions, fissures, diverticulae, cysts, fistulae, aneurysms, and other undesirable or unwanted depressions or openings that may exist within the body of an animal or mammal, including humans. For the treatment of conditions of the lumen, the MDCs are prepared as disclosed herein and then administered, e.g. via injection or intravenous delivery, to the lumenal tissue to fill or repair the void. The number of MDCs introduced is modulated to repair large or small voids in a soft tissue environment, as required.

Conditions of the sphincter: The MDCs and compositions thereof according to the present invention can also be used for the treatment of a sphincter injury, weakness, disease, or dysfunction in an animal or mammal, including humans. In particular, the MDCs are used to augment tissues of the esophageal, anal, cardiac, pyloric, and urinary sphincters. More specifically, the present invention provides soft tissue augmentation treatments for gastroesophageal reflux symptoms, and urinary and fecal incontinence. For the treatment of sphincter defects, the MDCs are prepared as described herein and then administered to the sphincter tissue, e.g. via injection, to provide additional bulk, filler, or support. The number of MDCs introduced is modulated to provide varying amounts of bulking material as required. For example, about 1 1.5×10⁶ MDCs are used to provide augmentation for an approximately 5 mm region of the gastroesophageal junction or an approximately 5-10 mm region of the anal sphincter (see Example 4).

Muscle augmentation and contractility: In yet another embodiment of the present invention, the MDCs and compositions thereof are used for the treatment of muscle conditions in a human or animal subject. In particular, the MDCs can be used to augment the skeletal or smooth muscles to treat weakness or dysfunction caused by injury, disease, inactivity, or anoxia- or surgery-induced trauma. More specifically, the present invention provides treatments for skeletal muscle weakness or dysfunction, such as a sports-related injury. The present invention also provides treatments for smooth muscle disease or dysfunction, such as heart failure, or injury associated with myocardial infarction.

For muscle augmentation or treatment of muscle-related conditions, the MDCs are prepared as described above and are administered, e.g. via injection, into muscle tissue to provide additional bulk, filler, or support. As is appreciated by the skilled practitioner, the number of MDCs introduced is modulated to provide varying amounts of bulking material, as needed or required. For example, about 1−1.5×10⁶ MDCs are injected for the augmentation of an approximately 5 mm region of heart tissue (see Example 7).

In addition, the MDCs and compositions thereof can be used to affect contractility in smooth muscle tissue, such as gastrointestinal tissue, esophageal tissue, and bladder tissue, as example. Indeed, muscle contractility was seen to be restored in cryodamaged bladder tissue after the introduction of muscle-derived progenitor cells, i.e., MDCs, as demonstrated in Example 6. Thus, the present invention also embraces the use of MDCs of the invention in restoring muscle contraction, and/or ameliorating or overcoming smooth muscle contractility problems, such decreased gastrointestinal motility, including the esophagus, stomach and intestine smooth muscle. A specific, yet nonlimiting example of a condition that the MDCs of the invention can improve, reduce, or correct is gastroparesis, i.e., poor motility and emptying of the stomach.

Conditions of the heart: In yet another embodiment, the MDCs and compositions thereof are used for the treatment or prevention of heart conditions in a human or mammal subject. These heart conditions include myocardial infarction, heart failure, Adams-Stokes disease, congenital heart disease, angina pectoris, arrhythmias, atrial fibrillation, bacterial endocarditis, cardiomyopathy, congestive heart failure, diastolic dysfunction, heart murmurs, and premature ventricular contractions. The MDCs and compositions thereof may be administered prophylactically to prevent these heart conditions from occurring, or may be administered after the pathology has occurred to repair damage to heart caused by the heart condition. For example, MDCs and compositions thereof may be administered to a human or animal that is at risk for a heart attack (myocardial infarction) before the heart attack occurs. The same or another human or animal may also be administered MDCs and compositions thereof to repair the heart after suffering a heart attack.

MDCs and compositions thereof to be used for the treatment or prevention of heart conditions may be isolated from human or animal skeletal muscle tissue using the methods described herein. The cells may be frozen after the slow adhering cells (MDC) are isolated for transport to a human or animal patient. In a preferred embodiment, skeletal muscle cells are isolated from a human or animal patient, placed at low temperature but not frozen (e.g. 4° C.) and collected for MDCs isolation. After MDCs and compositions thereof are isolated, the MDCs are expanded in cell culture, frozen and sent back to the patient for thawing and administration.

When administered the MDCs and compositions thereof may be injected directly into or just outside of the heart. When injected into the heart the MDCs and compositions thereof may be injected into any of the chambers of the heart or into the wall of the heart.

In a preferred embodiment of the invention, the MDCs are used for the treatment of myocardial infarction (MI), specifically in the acute phase. Treating post-MI damage acutely is essential to promote beneficial remodeling, while subsequently preventing deleterious remodeling and scarring, and preventing the deterioration of function. Greater benefit to MI patients can be made with MDCs in the acute phase with smaller cell doses.

Genetically Engineered Muscle-Derived Cells

In another aspect of the present invention, the MDCs of this invention may be genetically engineered to contain a nucleic acid sequence(s) encoding one or more active biomolecules, and to express these biomolecules, including proteins, polypeptides, peptides, hormones, metabolites, drugs, enzymes, and the like. Such MDCs may be histocompatible (autologous) or nonhistocompatible (allogeneic) to the recipient, including humans. These cells can serve as long-term local delivery systems for a variety of treatments, for example, for the treatment of such diseases and pathologies as cancer, transplant rejection, and the regeneration of muscle and nerve tissues, diabetes, liver failure, renal failure, neural defects and diseases such as Parkinson's disease, and to deliver a gene product to a site of tissue augmentation, or void filling, such as a therapeutic agent, as described herein.

Preferred in the present invention are autologous muscle-derived progenitor cells, which will not be recognized as foreign to the recipient. In this regard, the MDCs used for cell-mediated gene transfer or delivery will desirably be matched vis-a-vis the major histocompatibility locus (MHC or HLA in humans). Such MHC or HLA matched cells may be autologous. Alternatively, the cells may be from a person having the same or a similar MHC or HLA antigen profile. The patient may also be tolerized to the allogeneic MHC antigens. The present invention also encompasses the use of cells lacking MHC Class I and/or II antigens, such as described in U.S. Pat. No. 5,538,722.

The MDCs may be genetically engineered by a variety of molecular techniques and methods known to those having skill in the art, for example, transfection, infection, or transduction. Transduction as used herein commonly refers to cells that have been genetically engineered to contain a foreign or heterologous gene via the introduction of a viral or non-viral vector into the cells. Transfection more commonly refers to cells that have been genetically engineered to contain a foreign gene harbored in a plasmid, or non-viral vector. MDCs can be transfected or transduced by different vectors and thus can serve as gene delivery vehicles to transfer the expressed products into muscle.

Although viral vectors are preferred, those having skill in the art will appreciate that the genetic engineering of cells to contain nucleic acid sequences encoding desired proteins or polypeptides, cytokines, and the like, may be carried out by methods known in the art, for example, as described in U.S. Pat. No. 5,538,722, including fusion, transfection, lipofection mediated by the use of liposomes, electroporation, precipitation with DEAE-Dextran or calcium phosphate, particle bombardment (biolistics) with nucleic acid-coated particles (e.g., gold particles), microinjection, and the like.

Vectors for introducing heterologous (i.e., foreign) nucleic acid (DNA or RNA) into muscle cells for the expression of bioactive products are well known in the art. Such vectors possess a promoter sequence, preferably, a promoter that is cell-specific and placed upstream of the sequence to be expressed. The vectors may also contain, optionally, one or more expressible marker genes for expression as an indication of successful transfection and expression of the nucleic acid sequences contained in the vector.

Illustrative examples of vehicles or vector constructs for transfection or infection of the muscle-derived cells of the present invention include replication-defective viral vectors, DNA virus or RNA virus (retrovirus) vectors, such as adenovirus, herpes simplex virus and adeno-associated viral vectors. Adeno-associated virus vectors are single stranded and allow the efficient delivery of multiple copies of nucleic acid to the cell's nucleus. Preferred are adenovirus vectors. The vectors will normally be substantially free of any prokaryotic DNA and may comprise a number of different functional nucleic acid sequences. Examples of such functional sequences include polynucleotide, e.g., DNA or RNA, sequences comprising transcriptional and translational initiation and termination regulatory sequences, including promoters (e.g., strong promoters, inducible promoters, and the like) and enhancers which are active in muscle cells.

Also included as part of the functional sequences is an open reading frame (polynucleotide sequence) encoding a protein of interest; flanking sequences may also be included for site-directed integration. In some situations, the 5′-flanking sequence will allow homologous recombination, thus changing the nature of the transcriptional initiation region, so as to provide for inducible or noninducible transcription to increase or decrease the level of transcription, as an example.

In general, the nucleic acid sequence desired to be expressed by the muscle-derived progenitor cell is that of a structural gene, or a functional fragment, segment or portion of the gene, that is heterologous to the muscle-derived progenitor cell and encodes a desired protein or polypeptide product, for example. The encoded and expressed product may be intracellular, i.e., retained in the cytoplasm, nucleus, or an organelle of a cell, or may be secreted by the cell. For secretion, the natural signal sequence present in the structural gene may be retained, or a signal sequence that is not naturally present in the structural gene may be used. When the polypeptide or peptide is a fragment of a protein that is larger, a signal sequence may be provided so that, upon secretion and processing at the processing site, the desired protein will have the natural sequence. Examples of genes of interest for use in accordance with the present invention include genes encoding cell growth factors, cell differentiation factors, cell signaling factors and programmed cell death factors. Specific examples include, but are not limited to, genes encoding BMP-2 (rhBMP-2), IL-1Ra, Factor IX, and connexin 43.

As mentioned above, a marker may be present for selection of cells containing the vector construct. The marker may be an inducible or non-inducible gene and will generally allow for positive selection under induction, or without induction, respectively. Examples of commonly-used marker genes include neomycin, dihydrofolate reductase, glutamine synthetase, and the like.

The vector employed will generally also include an origin of replication and other genes that are necessary for replication in the host cells, as routinely employed by those having skill in the art. As an example, the replication system comprising the origin of replication and any proteins associated with replication encoded by a particular virus may be included as part of the construct. The replication system must be selected so that the genes encoding products necessary for replication do not ultimately transform the muscle-derived cells. Such replication systems are represented by replication-defective adenovirus constructed as described, for example, by G. Acsadi et al., 1994, Hum. Mol. Genet. 3:579 584, and by Epstein-Barr virus. Examples of replication defective vectors, particularly, retroviral vectors that are replication defective, are BAG, described by Price et al., 1987, Proc. Natl. Acad. Sci. USA, 84:156; and Sanes et al., 1986, EMBO J., 5:3133. It will be understood that the final gene construct may contain one or more genes of interest, for example, a gene encoding a bioactive metabolic molecule. In addition, cDNA, synthetically produced DNA or chromosomal DNA may be employed utilizing methods and protocols known and practiced by those having skill in the art.

If desired, infectious replication-defective viral vectors may be used to genetically engineer the cells prior to in vivo injection of the cells. In this regard, the vectors may be introduced into retroviral producer cells for amphotropic packaging. The natural expansion of muscle-derived progenitor cells into adjacent regions obviates a large number of injections into or at the site(s) of interest.

In another aspect, the present invention provides ex vivo gene delivery to cells and tissues of a recipient mammalian host, including humans, through the use of MDCs, e.g., early progenitor muscle cells, that have been virally transduced using an adenoviral vector engineered to contain a heterologous gene encoding a desired gene product. Such an ex vivo approach provides the advantage of efficient viral gene transfer, which is superior to direct gene transfer approaches. The ex vivo procedure involves the use of the muscle-derived progenitor cells from isolated cells of muscle tissue. The muscle biopsy that will serve as the source of muscle-derived progenitor cells can be obtained from an injury site or from another area that may be more easily obtainable from the clinical surgeon.

It will be appreciated that in accordance with the present invention, clonal isolates can be derived from the population of muscle-derived progenitor cells (i.e., PP6 cells) using various procedures known in the art, for example, limiting dilution plating in tissue culture medium. Clonal isolates comprise genetically identical cells that originate from a single, solitary cell. In addition, clonal isolates can be derived using FACS analysis as described above, followed by limiting dilution to achieve a single cell per well to establish a clonally isolated cell line. An example of a clonal isolate derived from the PP6 cell population is mc13, which is described in Example 9. Preferably, MDCs clonal isolates are utilized in the present methods, as well as for genetic engineering for the expression of one or more bioactive molecules, or in gene replacement therapies.

The MDCs are first infected with engineered viral vectors containing at least one heterologous gene encoding a desired gene product, suspended in a physiologically acceptable carrier or excipient, such as saline or phosphate buffered saline, and then administered to an appropriate site in the host. Consistent with the present invention, the MDCs can be administered to body tissues, including bone, epithelial tissue, connective tissue, muscle tissue, and various organ tissues such as those organs that are associated with the digestive system, cardiovascular system, respiratory system, reproductive system, urological system, and nervous system, as described above. The desired gene product is expressed by the injected cells, which thus introduce the gene product into the host. The introduced and expressed gene products can thereby be utilized to treat, repair, or ameliorate the injury, dysfunction, or disease, due to their being expressed over long time periods by the MDCs of the invention, having long-term survival in the host.

In animal model studies of myoblast-mediated gene therapy, implantation of 10⁶ myoblasts per 100 mg muscle was required for partial correction of muscle enzyme defects (see, J. E. Morgan et al., 1988, J. Neural. Sci. 86:137; T. A. Partridge et al., 1989, Nature 337:176). Extrapolating from this data, approximately 10¹² MDCs suspended in a physiologically compatible medium can be implanted into muscle tissue for gene therapy for a 70 kg human. This number of MDCs of the invention can be produced from a single 100 mg skeletal muscle biopsy from a human source (see below). For the treatment of a specific injury site, an injection of genetically engineered MDCs into a given tissue or site of injury comprises a therapeutically effective amount of cells in solution or suspension, preferably, about 10⁵ to 10⁶ cells per cm³ of tissue to be treated, in a physiologically acceptable medium.

EXAMPLES Example 1 MDC Enrichment, Isolation and Analysis

Enrichment and isolation of MDC: MDCs were prepared as described (U.S. Pat. No. 6,866,842 of Chancellor et al.). Muscle explants were obtained from the hind limbs of a number of sources, namely from 3-week-old mdx (dystrophic) mice (C57BL/10ScSn mdx/mdx, Jackson Laboratories), 4 6 week-old normal female SD (Sprague Dawley) rats, or SCID (severe combined immunodeficiency) mice. The muscle tissue from each of the animal sources was dissected to remove any bones and minced into a slurry. The slurry was then digested by 1 hour serial incubations with 0.2% type XI collagenase, dispase (grade II, 240 unit), and 0.1% trypsin at 37° C. The resulting cell suspension was passed through 18, 20, and 22 gauge needles and centrifuged at 3000 rpm for 5 minutes. Subsequently, cells were suspended in growth medium (DMEM supplemented with 10% fetal bovine serum, 10% horse serum, 0.5% chick embryo extract, and 2% penicillin/streptomycin). Cells were then preplated in collagen-coated flasks (U.S. Pat. No. 6,866,842 of Chancellor et al.). After approximately 1 hour, the supernatant was removed from the flask and re-plated into a fresh collagen-coated flask. The cells which adhered rapidly within this 1 hour incubation were mostly fibroblasts (U.S. Pat. No. 6,866,842 of Chancellor et al.). The supernatant was removed and re-plated after 30-40% of the cells had adhered to each flask. After approximately 5-6 serial platings, the culture was enriched with small, round cells, designated as PP6 cells, which were isolated from the starting cell population and used in further studies. The adherent cells isolated in the early platings were pooled together and designated as PP1-4 cells.

The mdx PP1-4, mdx PP6, normal PP6, and fibroblast cell populations were examined by immunohistochemical analysis for the expression of cell markers. The results of this analysis are shown in Table 1.

TABLE 1 Cell markers expressed in PP1-4 and PP6 cell populations. mdx PP1-4 mdx PP6 nor PP6 cells cells cells fibroblasts desmin +/− + + − CD34 − + + − Bcl-2 (−) + + − Flk-1 na + + − Sca-1 na + + − M-cadherin −/+ −/+ −/+ − MyoD −/+ +/− +/− − myogenin −/+ +/− +/− −

Mdx PP1-4, mdx PP6, normal PP6, and fibroblast cells were derived by preplating technique and examined by immunohistochemical analysis. “−” indicates less than 2% of the cells showed expression; “(−)”; “−/+” indicates 5-50% of the cells showed expression; “+/−” indicates ˜40-80% of the cells showed expression; “+” indicates that >95% of the cells showed expression; “nor” indicates normal cells; “na” indicates that the immunohistochemical data is not available.

It is noted that both mdx and normal mice showed identical distribution of all of the cell markers tested in this assay. Thus, the presence of the mdx mutation does not affect the cell marker expression of the isolated PP6 muscle-cell derived population.

MDCs were grown in proliferation medium containing DMEM (Dulbecco's Modified Eagle Medium) with 10% FBS (fetal bovine serum), 10% HS (horse serum), 0.5% chick embryo extract, and 1% penicillin/streptomycin, or fusion medium containing DMEM supplemented with 2% fetal bovine serum and 1% antibiotic solution. All media supplies were purchased through Gibco Laboratories (Grand Island, N.Y.).

Example 2 MDC Vectors and Transfection

Retrovirus and adenovirus vectors: The MFG-NB (N. Ferry et al., 1991, Proc. Natl. Acad. Sci. USA 88:8377 81) retroviral vector was used for the MDCs experiments. This vector contains a modified LacZ gene (NLS-LacZ) that includes a nuclear-localization sequence cloned from the simian virus (SV40) large T antigen transcribed from the long terminal repeat (LTR). The retroviral stock was grown and prepared as previously described (J. C. van Deutekom et al., 1998, Neuromuscul. Disord. 8:135 48). The retrovirus was titered to 1×10⁷−1×10⁹ cfu/ml.

An adenovirus vector was also used. This vector contained the LacZ gene under the control of the human cytomegalovirus (HuCMV) promoter (J. Huard et al., 1994, Hum Gene Ther 5:949 58). The E1 E3 deleted recombinant adenovirus was obtained through Dr. I. Kovesdi (Gene Vec Inc., Rockville, Md.).

Viraltransduction of MDC: For viral transduction, MDCs were plated at a density of 1−1.5×10⁶ in T 75 flasks. PP6 MDCs were washed in HBSS (Hank's Balanced Salt Solution) and incubated with either retrovirus (1×10⁷-1×10⁹ cfu/ml) or adenovirus (1×10⁹ cfu/ml) suspensions in 5 ml of DMEM containing 8 μg/ml Polybrene™ (Abbott Laboratories, Chicago, Ill.) for 4 h at 37° C. Virally transduced MDCs were grown in 10 ml of proliferation medium for 24 h at 37° C. MDCs were then rinsed with HBSS and enzymatically digested with 0.25% trypsin for 1 minute. The treated, virally transduced MDCs were centrifuged for 5 minutes at 3,500 rpm, and the pellet was resuspended in 20 μl of HBSS.

Example 3 Soft Tissue Augmentation of the Skin

MDCs and collagen injection: SD rats were prepared for surgery by anesthetizing with halothane using standard methods, and washing the surgical site with Betadine® solution. The skin of the lower abdomen was injected with either 10 microliters (μl) of a MDC suspension in HBSS (approximately 1−1.5×10⁶ cells), 10 μl of commercially available bovine collagen (Contigen™; C. R. Bard, Covington, Ga.), or 10 μl of sterile saline using a Hamilton microsyringe. At 5 days, 2 weeks and 4 weeks post-injection, the area surrounding each injection site was excised, prepared for histochemical analysis, examined microscopically, and photographed. Histochemical analysis included hematoxylin, eosin, or trichrome staining.

The results demonstrate that MDCs were viable for up to at least 4 weeks following injection into skin tissue, with no evidence of inflammation of the tissue at the injection site (FIGS. 1D-1F). In contrast, collagen was not visible at 2 weeks following injection into skin tissue (FIGS. 1B and 1C). Thus, MDC compositions can be used as skin augmentation materials for use, for example, in cosmetic and aesthetic applications or surgery. This is an unexpected finding, since it was previously believed that transplanted muscle cells needed surrounding host muscle fibers with which to attach in order to survive. The survival of the MDCs of the present invention following injection into non-muscle tissue is further demonstrated in Examples 8 and 9.

Example 4 Soft Tissue Augmentation of the Gastroesophageal Junction and Anal Sphincter

SD rats were prepared for surgery as described above. A midline abdomen incision was made to expose the gastroesophageal junction and anal sphincter. The soft tissue was injected with 10 μl of a suspension of muscle-derived progenitor cells of in HBSS (1−1.5×10⁶ cells) using a Hamilton microsyringe. At day 3 post-injection, the area surrounding each injection site was excised, prepared for histochemical analysis, stained for β-galactosidase to determine the location and viability of the cells carrying the LacZ marker, examined microscopically, and photographed. Results of these experiments demonstrate that MDC compositions can be used as esophageal and anal sphincter bulking materials (FIGS. 2A and 2B) for the treatment of gastroesophageal reflux or fecal incontinence symptoms or conditions.

Example 5 Soft Tissue Augmentation of Vesico-Ureteral Junction

SD rats were prepared for surgery as described above. A midline abdomen incision was made to expose the ureteral-bladder (vesico-ureteral) junction. The tissue was injected with 10 μl of MDC suspension in HBSS (1−1.5×10⁶ cells) using a Hamilton microsyringe. At 3 days post-injection, the area surrounding each injection site was excised, prepared for histological analysis, stained for β-galactosidase to determine the location and viability of the cells carrying the LacZ marker, examined microscopically, and photographed. These results demonstrate that MDC-based compositions can be used as utereral-bladder augmentation materials (FIGS. 3A and 3B) for the treatment of vesico-ureteral reflux symptoms or conditions.

Example 6 MDC Treatment of Cryodamaged Bladder Tissue

Cryoinjury and MDC transplantation: SD rats were prepared for surgery as described above. A low midline incision was made to expose the bladder and urethra. The bladder was then filled with 1 ml saline. Cryodamage was performed with an 8 mm diameter aluminum rod chilled on dry ice. The chilled probe was placed against one side of the bladder wall for 15 or 30 seconds (referred to as “mild” or “severe” damage, respectively). Immediately following cryoinjury, one severe damage group was injected with muscle-derived cells of the invention (1−1.5×10⁶ of cells in 15 μl HBSS), while a control severe damage group was injected with HBSS (15 μl) (n=3 per group). One week following cryoinjury, the other mild and severe damage groups were injected with an MDC suspension in 50 μl HBSS (2−3×10⁶ cells), while control mild and severe damage groups were injected with 50 μl HBSS (n=4 per group). For each group, injections were made into the center of the injured region using a 30-gauge needle and a Hamilton microsyringe.

Immunohistochemical staining for smooth muscle actin (α-SM actin): To prepare samples for immunohistochemical analysis, tissues or cell samples were fixed in cold acetone at −20° C. for 2 minutes, and blocked with 5% HS for 1 hour. The samples were incubated overnight at room temperature in a humidity chamber with mouse monoclonal anti-smooth muscle actin primary antibodies (Cat. # F-3777; Sigma Chemical Co., St. Louis, Mo.) (1:400 dilution in PBS pH 7.4). The samples were then washed 3 times with PBS, and incubated with anti-mouse IgG secondary antibodies conjugated with the Cy3 fluorochrome (Sigma Chemical Co.) (1:200 dilution in PBS pH 7.4).

Immunohistochemical staining for fast myosin heavy chain (Fast MyHC): Tissues or cell samples were fixed in cold acetone at −20° C. for 2 minutes and blocked with 5% HS for 1 hour. The samples were then incubated overnight at room temperature in a humidity chamber with mouse monoclonal anti-skeletal myosin (fast) primary antibodies (Cat. # M4276; Sigma Chemical Co.) (1:400 dilution in PBS pH 7.4). The samples were then washed 3 times with PBS, and incubated with Cy3 conjugated anti-mouse IgG secondary antibodies (Sigma Chemical Co.) (1:200 dilution in PBS pH 7.4).

Cell culture: Muscle derived progenitor cells as prepared in Example 1 were plated in 35 mm collagen-coated dishes in proliferation medium. After 24 hours, the proliferation medium was replaced with fusion medium. The cells were maintained in fusion medium with daily medium changes until the MDCs differentiated into myotubes.

Contractility studies: Two weeks after the MDC injection, the animals were euthanized and used to prepare bladder strips. Two strips were prepared from each bladder, and both strips were cut to extend along the circumference of the bladder. The bladder strips were mounted in a tissue bath and subjected to neural contractions (20 Hz, 10 and 80 shocks), which were recorded and analyzed as described below.

Tissue harvest and histology: SD rats were euthanized and samples of the tissue surrounding the injection site were removed. The samples were flash frozen using 2-methylbutane pre-cooled in liquid nitrogen. Histochemical analysis of the samples included hematoxylin and eosin staining. The samples were stained, examined microscopically, and photographed. Each cryostat section measured 10 μm in thickness.

Electrostimulation of bladder smooth muscle tissue: The animal was euthanized and the bladder was quickly removed. Two strips covering the circumference of the bladder wall were obtained from each bladder. The strips were mounted in 5 ml organ baths containing Kreb's solution (113 mmol/l NaCl, 4.7 mmol/l KCl, 1.25 mmol/l CaCl₂, 1.2 mmol/l MgSO₄, 25 mmol/l NaHCO₃, 1.2 mmol/l KH₂PO₄, and 11.5 mmol/l glucose) aerated with 95% O₂ and 5% CO₂. The initial tension was set to 10 mN, and isometric contractions were measured with strain-gauge transducers coupled with a TBM4 strain gauge amplifier (World Precision Instruments). Contraction measurements were compiled using a data acquisition program (Windaq, DATAQ Instruments, Inc., Akron, Ohio). The sampling rate per channel was set to 100 Hz. The amplitude of the contractions was computed using a calculation program (WindaqEx, DATAQ Instruments, Inc.). Following a 20 minutes equilibration period, electrical field stimuli were applied through two platinum wire electrodes separated by 4 cm at the top and the bottom of the organ bath. The temperature was maintained at 37° C. throughout the experiment.

Chemical stimulation of bladder smooth muscle tissue: The bladder strips were stimulated with square wave pulses of 0.25 msec duration with maximal voltage (100 V) and a frequency response curve constructed using 10 or 80 shocks at 1, 2, 5, 10, 20, or 40 Hz. Following electrostimulation, 5, 10, or 20 μM carbachol was added to the bladder strips to induce contractions. In parallel experiments, 1 μM atropine was added, electrostimulation was applied as above, and 50 μM methylene ATP was added to induce contractions.

Staining for innervation: Acetylcholine (Ach) staining was used to assess the reinnervation of MDCs in smooth muscle. Ach is a stain for the neuromuscular junction that indicates the presence of nerve endings. Following MDC injection, tissue was excised at day 3, 15, 30, or after 6 months, stained for Ach, observed by microscopy, and photographed.

Statistical analysis: Values are reported as means.+/−.standard deviations. A “P” value of less than 0.05 was considered statistically significant. Student's test was used.

MDC differentiation: Muscle derived progenitor cells as prepared in Example 1 were evaluated for cellular differentiation. Alpha-SM actin is the earliest known marker for the smooth muscle cell phenotype (K. M. McHugh, 1995, Dev. Dyn. 204:278-90), and the main marker of the myofibroblastic phenotype (I. Darby et al., 1990, Lab. Invest. 63:21-9). During muscle cell differentiation, expression of α-SM actin decreases, while fast MyHC expression increases. Histochemical analysis of MDC-treated bladder tissues utilizing α-SM actin and fast MyHC markers demonstrates the differentiation of MDCs following injection into site of cryoinjury. At day 5 following injection into cryodamaged bladder tissue, several MDCs (at least 20%) show α-SM actin staining (FIG. 5B), indicating that the cells are still undifferentiated. After 6 months following injection, however, virtually all MDCs have differentiated into myotubes or myofibers, as shown by an decrease in α-SM actin staining (FIG. 5F), with a concomitant increase in fast MyHC staining (FIG. 5I).

Muscle reinnervation: Because acetylcholine (Ach) is present at the neuromuscular junction, it can serve as an indicator of muscle innervation. Histochemical analysis of MDC-treated bladder tissues utilizing the Ach marker demonstrates the reinnervation of the MDCs following injection into sites of cryodamage. At day 3 following injection into cryodamaged bladder tissue the injected MDCs show minimal innervation, as indicated by relatively low levels of Ach staining (FIG. 6A). At day 15 post-injection, increased levels of innervation are observed, as indicated by increased levels of Ach staining (FIG. 6B). At day 30 post-injection, still more Ach staining is observed (FIG. 6C), indicative of further increases in innervation. At 6 months following injection, extensive innervation is observed, as indicated by substantial Ach staining throughout the MDC injected area viewed at low magnification (FIG. 6D). These results indicate that the pelvic nerve is growing into the MDC injected area of the bladder, and suggest that the MDCs can improve the contractility and function of the injected tissue.

Contractility Physiology studies: To determine whether injected MDCs improved the function of the treated bladder tissues, several contractility studies were completed (see above). Table 2 presents the data showing the contractile parameters of bladder muscle following cryoinjury with or without MDC injections.

TABLE 2 Contractile parameters of bladder muscle following cryoinjury. Group Contraction amplitude (mN/mg) Velocity (contraction) (mN/s) No. of No. 20 Hz/10 shocks 20 Hz/80 shocks 20 Hz/10 shocks 20 Hz/80 shocks specimens 1 Sham 0.375 ± 0.24 0.697 ± 0.46 18.08 ± 8.15 15.56 ± 8.39 6 MDC 0.368 ± 0.26 0.812 ± 0.31 16.23 ± 10.3 16.38 ± 7.54 6 2 Sham 0.427 ± 0.17 0.966 ± 0.31 22.96 ± 8.93 24.56 ± 5.03 8 MDC 0.539 ± 0.24 1.161 ± 0.55 27.86 ± 14.08 30.59 ± 13.05 8 3 Sham 0.389 ± 0.14* 0.708 ± 0.26** 25.70 ± 5.87 24.24 ± 6.38 8 MDC 0.564 ± 0.16* 1.139 ± 0.29** 30.59 ± 17.8 29.31 ± 15.3 8 4 Normal 0.927 ± 0.23 1.748 ± 0.52 34.23 ± 8.82 29.05 ± 7.06 6

*p<0.05, **P<0.01 Values are means .+/−. standard deviations. For statistical analysis, Student's test was performed for control and MDC injection groups. Group No. 1: severe damage group with immediate MDC injections following cryoinjury. Group No. 2: mild damage group with MDC injections one week following cryodamage. Group No. 3: severe damage group with MDC injections one week following cryodamage. Group No. 4: normal bladder tissue.

The severe damage group injected with MDCs immediately following cryoinjury (Group 1) showed similar contractility as the control (sham) group (compare contractility levels shown in sham and MDCs rows in Group 1, Table 2). However, the severe damage group injected with MDCs one week following the cryodamage (Group 3) showed increased contraction amplitude (145% and 161% of the control bladder at 20 Hz/10 shocks and 20 Hz/80 shocks, respectively) compared with the control group (compare contractile amplitude levels shown in sham and MDC rows indicated with asterisks in Table 2). Similarly, the severe damage group injected with MDCs one week following the cryodamage (Group 3) showed increased contraction velocity (119% and 121% of that of the control strip at 20 Hz/10 shocks and 20 Hz/80 shocks, respectively) compared with the control group (compare contractile velocity values in sham and MDCs rows in Group 3, Table 2). The mild damage group injected with MDCs one week following the cryodamage (Group 2) also showed increased contraction amplitude and velocity compared to the control group (compare contractility levels shown in sham and MDCs rows in Group 2, Table 2). The results of these studies show that MDC injections can restore contractility to cryodamaged bladder muscle tissue, and indicate that MDC-based compositions can be utilized for the treatment of urinary incontinence.

Example 7 Soft Tissue Augmentation of the Myocardium

SD rats were prepared for surgery as described above. A thoracic incision was made to expose the heart. The ventricular wall was injected with 10 μl of MDC suspension in HBSS (1−1.5×10⁶6 cells) using a Hamilton microsyringe. At day 3, the area surrounding each injection site was excised, prepared for histochemical analysis, stained for β-galactosidase to determine the location and viability of the cells carrying the LacZ marker, examined microscopically, and photographed. The results of these experiments demonstrate that MDC compositions can be used as myocardial soft tissue augmentation materials (FIGS. 7A and 7B) for the treatment of injury or weakness secondary to heart failure or myocardial infarction.

Example 8 MDC Injection into Liver, Spleen, and Spinal Cord Tissues

SD rats were prepared for surgery as described above. A midline abdomen incision was made to expose the liver and spleen. Both sites were injected with 10 μl of MDC suspension in HBSS (1−1.5×10⁶ cells) using a Hamilton microsyringe. At the same time, a midline back incision and a partial laminectomy was made to expose the spinal cord. Spinal cord tissues at level T10 were then injected with the MDC suspension in HBSS as done for the liver and spleen tissues. At day 4, the area surrounding each injection site was excised, prepared histochemical analysis, stained for β-galactosidase to determine the location and viability of the cells carrying the LacZ marker, examined _(microscopically), and photographed. These experiments show that MDC compositions can be used as liver, spleen, and spinal cord soft tissue augmentation materials (FIGS. 8A 8B, 9A 9B, and 10A 10B) to treat various liver, spleen, and spinal cord injuries, diseases, or dysfunctions.

Example 9 MDC Treatment of Bone Defects

Isolation of muscle derived cells: MDCs were obtained from mdx mice as described in Example 1.

Clonal isolation of PP6 muscle-derived progenitor cells: To isolate clones from the PP6 cell population, PP6 cells were transfected with a plasmid containing the LacZ, mini-dystrophin, and neomycin resistance genes. Briefly, a SmaI/Sa/I fragment containing the neomycin resistance gene from pPGK-NEO was inserted into the SmaI/Sa/I site in pIEPlacZ plasmid containing the LacZ gene, creating the pNEOlacZ plasmid. The XhoI/Sa/I fragment from DysM3 which contains the short version of the dystrophin gene (K. Yuasa et al., 1998, FEBS Left. 425:329 336; gift from Dr. Takeda, Japan) was inserted into Sa/I site in the pNEOlacZ to generate a plasmid which contains the mini-dystrophin, LacZ, and neomycin resistance genes. The plasmid was linearized by Sa/I digestion prior to transfection.

PP6 cells were transfected with 10 μg of the linear plasmid containing mini-dystrophin, LacZ, and neomycin resistance gene using the Lipofectamine Reagent (Gibco BRL) according to the manufacturer's instructions. At 72 hours after transfection, cells were selected with 3000 μg/ml of G418 (Gibco BRL) for 10 days until discrete colonies appeared. Colonies were then isolated and expanded to obtain a large quantity of the transfected cells, and then tested for expression of LacZ. One of these PP6-derived clones, mc13, was used for further study.

Immunohistochemistry: PP6, mc13, and mouse fibroblast cells were plated in a 6-well culture dish and fixed with cold methanol for 1 minute. Cells were then washed with phosphate buffered saline (PBS), and blocked with 5% horse serum at room temperature for 1 hour. The primary antibodies were diluted in PBS as follows: anti-desmin (1:100, Sigma), biotinylated anti-mouse CD34 (1:200, Pharmingen), rabbit anti-mouse Bcl-2 (1:500, Pharmingen), rabbit anti-mouse M-cadherin (1:50, gift from Dr. A. Wernig), mouse anti-mouse MyoD (1:100, Pharmingen), mouse anti-rat myogenin (1:100, Pharmngen), rabbit anti-mouse Flk-1 (1:50, Research Diagnostics), and biotinylated Sca-1 (1:100, Pharmingen). Cells were incubated with the primary antibodies at room temperature overnight. Cells were then washed and incubated with the appropriate biotinylated secondary antibodies for 1 hour at room temperature. Subsequently, the cells were rinsed with PBS then incubated at room temperature with 1/300 streptavidin conjugated with Cy3 fluorochrome for 1 hour. Cells were then analyzed by fluorescence microscopy. For each marker, the percentage of stained cells was calculated for 10 randomly chosen fields of cells.

Cryosections of muscle samples from a four week old normal mouse (C-57 BL/6J, Jackson Laboratories) were fixed with cold acetone for 2 minutes and pre-incubated in 5% horse serum diluted in PBS for 1 hour. For CD34, Bcl-2, and collagen type IV, the following primary antibodies were used: biotin anti-mouse CD34 (1:200 in PBS, Pharmingen), rabbit anti-mouse Bcl-2 (1:1000, Pharmingen), and rabbit anti-mouse collagen type IV (1:100 in PBS, Chemicon). For dystrophin staining, sheep-anti-human DY10 antibody (1:250 dilution in PBS) was used as the primary antibody, and the signal was amplified using anti-sheep-biotin (1:250 dilution in PBS), and streptavidin-FITC (1:250 dilution in PBS).

Stimulation with rhBMP-2, osteocalcin staining, and alkaline phosphatase assay: Cells were plated in triplicate at a density of 1 2×10⁴ cells per well in 12 well collagen-coated flasks. The cells were stimulated by the addition of 200 ng/ml recombinant human BMP-2 (rhBMP-2) to the growth medium. The growth medium was changed on days 1, 3, and 5 following the initial plating. A control group of cells was grown in parallel without added rhBMP-2. After 6 days with or without rhBMP-2 stimulation, cells were counted using a microcytometer and analyzed for osteocalcin and alkaline phosphatase expression. For osteocalcin staining, cells were incubated with goat anti-mouse osteocalcin antibodies (1:100 in PBS, Chemicon), followed by incubation with anti-goat antibodies conjugated with the Cy3 fluorochrome. To measure alkaline phosphatase activity, cell lysates were prepared and analyzed using a commercially available kit that utilizes color change in the reagent due to the hydrolysis of inorganic phosphate from p-nitrophenyl phosphate (Sigma). The resulting color change was measured on a spectrophotometer, and the data were expressed as international units ALP activity per liter normalized to 10⁶ cells. Statistical significance was analyzed using student's t-test (p<0.05).

In vivo differentiation of mc13 cells in myogenic and osteogenic lineages—Myogenic: The mc13 cells (5×10⁵ cells) were injected intramuscularly in the hind limb muscle of mdx mice. The animals were sacrificed at 15 days post-injection, and the injected muscle tissue was frozen, cryostat sectioned, and assayed for dystrophin (see above) and LacZ expression. To test for LacZ expression, the muscle sections were fixed with 1% glutaraldehyde and then were incubated with X-gal substrate (0.4 mg/ml 5-bromochloro-3 indolyl-β-D-galactoside (Boehringer-Mannheim), 1 mM MgCl₂, 5 mM K₄Fe(CN)₆, and 5 mM K₃Fe(CN)₆ in phosphate buffered saline) for 1-3 hours. Sections were counter-stained with eosin prior to analysis. In parallel experiments, mc13 cells (5×10⁵ cells) were injected intravenously in the tail vein of mdx mice. The animals were sacrificed at 7 days post-injection and hind limbs were isolated and assayed for the presence of dystrophin and β-galactosidase as described.

Osteogenic: To construct the adenovirus BMP-2 plasmid (adBMP-2), the rhBMP-2 coding sequence was excised from the BMP-2-125 plasmid (Genetics Institute, Cambridge, Mass.) and subcloned into a replication defective (E1 and E3 gene deleted) adenoviral vector containing the HuCMV promoter. Briefly, the BMP-2-125 plasmid was digested with Sa/I, resulting in a 1237 base pair fragment containing the rhBMP-2 cDNA. The rhBMP-2 cDNA was then inserted into the Sa/I site of the pAd.lox plasmid, which placed the gene under the control of the HuCMV promoter. Recombinant adenovirus was obtained by co-transfection of pAd.lox with psi-5 viral DNA into CREW cells. The resulting adBMP-2 plasmid was stored at −80° C. until further use.

Mc13 cells were trypsinized and counted using a microcytometer prior to infection. Cells were washed several times using HBSS (GibcoBRL). Adenovirus particles equivalent to 50 multiplicity of infection units were premixed into HBSS then layered onto the cells. Cells were incubation at 37° C. for 4 hours, and then incubated with an equal volume of growth medium. Injections of 0.5−1.0×10⁶ cells were performed using a 30-gauge needle on a gas-tight syringe into exposed triceps surae of SCID mice (Jackson Laboratories). At 14-15 days, the animals were anesthetized with methoxyflurane and sacrificed by cervical dislocation. The hind limbs were analyzed by radiography. Subsequently, the triceps surae were isolated and flash frozen in 2-methylbutane buffered in phosphate buffered saline, and pre-cooled in liquid nitrogen. The frozen samples were cut into 5 10 μm sections using a cryostat (Microm, HM 505 E, Fisher Scientific) and stored at −20° C. for further analysis.

RT-PCR analysis: Total RNA was isolated using TRIzol reagent (Life Technologies). Reverse transcription was carried out using SuperScript™ Preamplification System for First Strand cDNA Synthesis (Life Technologies) according to the instructions of the manufacturer. Briefly, 100 ng random hexamers were annealed to 1 μg total RNA at 70° C. for 10 minutes, and then chilled on ice. Reverse transcription was carried out with 2 μl 10XPCR buffer, 2 μl 25 mM MgCl₂, 1 μl 10 mM dNTP mix, 2 μl 0.1 M DTT, and 200 U superscript 11 reverse transcriptase. The reaction mixture was incubated for 50 minutes at 42° C.

Polymerase chain reaction (PCR) amplification of the targets was performed in 50 μl reaction mixture containing 2 μl of reverse transcriptase reaction product, 100 μl (5 U) Taq DNA polymerase (Life Technologies), and 1.5 mM MgCl₂. The CD34 PCR primers were designed using Oligo software and had the following sequences: CD34 UP: TAA CTT GAC TTC TGC TAC CA (SEQ ID NO:1); and CD34 DOWN: GTG GTC TTA CTG CTG TCC TG (SEQ ID NO:2). The other primers were designed according to previous studies (J. Rohwedel et al., 1995, Exp. Cell Res. 220:92 100; D. D. Comelison et al., 1997, Dev. Biol. 191:270 283), and had the following sequences: C-MET UP: GAA TGT CGT CCT ACA CGG CC (SEQ ID NO:3); C-MET DOWN: CAC TAC ACA GTC AGG ACA CTG C (SEQ ID NO:4); MNF UP: TAC TTC ATC AAA GTC CCT CGG TC (SEQ ID NO:5); MNF DOWN: GTA CTC TGG AAC AGA GGC TAA CTT (SEQ ID NO:6); BCL-2 UP: AGC CCT GTG CCA CCA TGT GTC (SEQ ID NO:7); BCL-2 DOWN: GGC AGG TTT GTC GAC CTC ACT (SEQ ID NO:8); MYOGENIN UP: CAA CCA GGA GGA GCG CGA TCT CCG (SEQ ID NO:9); MYOGENIN DOWN: AGG CGC TGT GGG AGT TGC ATT CAC T (SEQ ID NO:10); MYOD UP: GCT CTG ATG GCA TGA TGG ATT ACA GCG (SEQ ID NO:11); and MYOD DOWN: ATG CTG GAC AGG CAG TCG AGG C (SEQ ID NO: 12).

The following PCR parameters were used: 1) 94° C. for 45 seconds; 2) 50° C. for 60 seconds (CD34) or 60° C. for 60 seconds (for myogenin and c-met); and 3) 72° C. for 90 seconds for 40 cycles. PCR products were checked by agarose-TBE-ethidium bromide gels. The sizes of the expected PCR products are: 147 bp for CD34; 86 bp for myogenin; and 370 bp for c-met. To exclude the possibility of genomic DNA contamination, two control reactions were completed: 1) parallel reverse transcription in the absence of reverse transcriptase, and 2) amplification of β-actin using an intron-spanning primer set (Clonetech).

Skull defect assay: Three 6-8 week old female SCID mice (Jackson Laboratories) were used in control and experimental groups. The animals were anesthetized with methoxyflurane and placed prone on the operating table. Using a number 10 blade, the scalp was dissected to expose the skull, and the periosteum was stripped. An approximately 5 mm full-thickness circular skull defect was created using a dental burr, with minimal penetration of the dura. A collagen sponge matrix (Helistat™, Colla-T c, Inc.) was seeded with 0.5−1.0×10⁶ MDCs either with or without adBMP-2 transduction, and placed into the skull defect. The scalp was closed using a 4-0 nylon suture, and the animals were allowed food and activity. After 14 days, the animals were sacrificed, and the skull specimens were observed and then analyzed microscopically. For von Kossa staining, skull specimens were fixed in 4% formaldehyde and then soaked in 0.1 M AgNO₃ solution for 15 minutes. The specimens were exposed to light for at least 15 minutes, washed with PBS, and then stained with hematoxylin and eosin for viewing.

Fluorescence in situ hybridization using Y-probes: The cryosections were fixed for 10 minutes in 3:1 methanol/glacial acetic acid (v:v) and air dried. The sections were then denatured in 70% formamide in 2×SSC (0.3 M NaCl, 0.03 M NaCitrate) pH 7.0 at 70° C. for 2 minutes. Subsequently, the slides were dehydrated with a series of ethanol washes (70%, 80%, and 95%) for 2 minutes at each concentration. The Y-chromosome specific probe (Y. Fan et al., 1996, Muscle Nerve 19:853 860) was biotinylated using a BioNick kit (Gibco BRL) according to the manufacturer's instructions. The biotinylated probe was then purified using a G-50 Quick Spin Column (Boehringer-Mannheim), and the purified probe was lyophilized along with 5 ng/ml of sonicated herring sperm DNA. Prior to hybridization, the probe was re-suspended in a solution containing 50% formamide, 1×SSC, and 10% dextran sulfate. After denaturation at 75° C. for 10 minutes, the probe was placed on the denatured sections and allowed to hybridize overnight at 37° C. After hybridization, the sections were rinsed with 2×SSC solution pH 7.0 at 72° C. for 5 minutes. The sections were then rinsed in BMS solution (0.1 M NaHCO₃, 0.5 M NaCl, 0.5% NP-40, pH 8.0). The hybridized probe was detected with fluorescein labeled avidin (ONCOR, Inc). The nuclei were counter-stained with 10 ng/ml ethidium bromide in Vectashield mounting medium (Vector, Inc).

Marker analysis of mc13 cells: The biochemical markers expressed by mc13, PP6, and fibroblast cells were analyzed using RT-PCR and immunohistochemistry. Table 3 (below) shows that mc13 cells expressed Flk-1, a mouse homologue of the human KDR gene, which was recently identified as a marker of hematopoietic cells with stem cell-like characteristics (B. L. Ziegler et al., supra), but did not express CD34 or CD45. However, other clonal isolates derived from the PP6 MDCs of the present invention expressed CD34, as well as other PP6 cell markers. It will be appreciated by those skilled in the art that the procedures described herein can be used to clone out the PP6 muscle-derived progenitor cell population and obtain clonal isolates that express cell markers characteristic of the muscle-derived progenitor cells. Such clonal isolates can be used in accordance with the methods of the invention. For example, the clonal isolates express progenitor cell markers, including desmin, CD34, and Bcl-2. Preferably, the clonal isolates also express the Sca-1 and Flk-1 cell markers, but do not express the CD45 or c-Kit cell markers.

TABLE 3 Cell markers expressed by mdx PP6, mdx mc13, and fibroblast cells. PP6 cells MC13 cells Fibroblasts imm RT-PCR imm RT-PCR imm RT-PCR desmin + na + na − na CD34 + + − − − − Bcl-2 + na +/− na − na Flk-1 + na + na − na Sca-1 + na + na − na M-cadherin −/+ na + na − na Myogenin +/− + +/− + − − c-met na + na + na − MNF na + na + na − MyoD −/+ + na + na − c-Kit − na − na na na CD45 − na − na na na

Cells were isolated as described above and examined by immunohistochemical analysis. “−” indicates that 0% of the cells showed expression; “+” indicates that >98% of the cells showed expression; “+/−” indicates that 40 80% of the cells showed expression; “−/+” indicates that 5 30% of the cells showed expression; “na” indicates that the data is not available.

In vivo localization of CD34⁺ and Bcl-2⁺ cells: To identify the location of CD34⁺ and Bcl-2⁺ cells in vivo, muscle tissue sections from the triceps surae of normal mice were stained using anti-CD34 and anti-Bcl-2 antibodies. The CD34 positive cells constituted a small population of muscle derived cells (FIG. 12A) that were also positive for desmin (FIG. 12B). Co-staining the CD34+, desmin+ cells with anti-collagen type IV antibody localized them within the basal lamina (FIGS. 12B and 12D). As indicated by the arrowheads in FIGS. 12A D, small blood vessels were also positive for CD34 and collagen type IV, but did not co-localize with the nuclear staining. The expression of CD34 by vascular endothelial cells has been shown in previous studies (L. Fina et al., supra). The Bcl-2+, desmin+ cells were similarly identified (FIGS. 12E 12H) and localized within the basal lamina (FIGS. 12F and 12H). The sections were also stained for M-cadherin to identify the location of satellite cells (FIG. 12I). The satellite cells were identified at similar locations as CD34+, desmin+, or Bcl-2+, desmin+ cells (arrow, FIG. 12I). However, multiple attempts to co-localize CD34 or Bcl-2 with M-cadherin were unsuccessful, suggesting that M-cadherin expressing cells do not co-express either Bcl-2 or CD34. This is consistent with PP6 cells expressing high levels of CD34 and Bcl-2, but expressing minimal levels of M-cadherin, as disclosed herein.

In vitro differentiation of clonal muscle progenitor cells into osteogenic lineage: Mc13 cells were assessed for osteogenic differentiation potential by stimulation with rhBMP-2. Cells were plated on 6-well culture dishes and grown to confluency in the presence or absence of 200 ng/ml rhBMP-2. Within 34 days, mc13 cells exposed to rhBMP-2 showed dramatic morphogenic changes compared to cells without rhBMP-2. In the absence of rhBMP-2, mc13 cells began to fuse into multinucleated myotubes (FIG. 13A). When exposed to 200 ng/ml rhBMP-2, however, cells remained mononucleated and did not fuse (FIG. 13B). When cell density reached >90% confluency, the untreated culture fused to form multiple myotubes (FIG. 13C), while the treated cells became circular and hypertrophic (FIG. 13D). Using immunohistochemistry, these hypertrophic cells were analyzed for the expression of osteocalcin. Osteocalcin is a matrix protein that is deposited on bone, specifically expressed by osteoblasts. In contrast to the untreated group, the rhBMP-2 treated hypertrophic cells showed significant expression of osteocalcin (FIG. 13E), thus suggesting that mc13 cells are capable of differentiating into osteoblasts upon exposure to rhBMP-2.

Mc13 cells were then analyzed for expression of desmin following rhBMP-2 stimulation. Newly isolated mc13 cells showed uniform desmin staining (FIGS. 14A and 14B). Within 6 days of exposure to rhBMP-2, only 30-40% of mc13 cells showed desmin staining. In the absence of rhBMP-2 stimulation, approximately 90-100% of mc13 cells showed desmin staining (FIG. 14C). This result suggests that stimulation of mc13 cells with rhBMP-2 results in the loss of myogenic potential for these cells.

In addition, mc13 cells were analyzed for the expression of alkaline phosphatase following rhBMP-2 stimulation. Alkaline phosphatase has been used as a biochemical marker for osteoblastic differentiation (T. Katagiri et al., 1994, J. Cell Biol. 127:1755 1766). As shown in FIG. 14D, alkaline phosphatase expression of mc13 cells was increased more than 600 fold in response to rhBMP-2. PP1 4 cells, used as a control, did not show increased alkaline phosphatase activity in response to rhBMP-2 (FIG. 14D). Taken together, these data demonstrate that cells of a PP6 clonal isolate, e.g., mc13 cells, can lose their myogenic markers and differentiate through the osteogenic lineage in response to rhBMP-2 exposure in vitro.

In vivo differentiation of mc13 cells into myogenic and osteogenic lineages: To determine whether mc13 cells were capable of differentiating through the myogenic lineage in vivo, the cells were injected into the hind limb muscle tissue of mdx mice. The animals were sacrificed 15 days following injection, and their hind limbs were harvested for histological and immunohistochemical analysis. Several myofibers showed LacZ and dystrophin staining in the region surrounding the injection site (FIGS. 15A and 15B), indicating that mc13 cells can differentiate through the myogenic lineage in vivo and enhance muscle regeneration and restore dystrophin in the dystrophic muscle.

In a parallel experiment, mc13 cells were injected intravenously into the tail vein of mdx mice. The animals were sacrificed at 7 days post-injection, and the hind limb muscles were harvested for histological and immunohistochemical analysis. Several hind limb muscle cells showed LacZ and dystrophin staining (FIGS. 15C 15D; see also “*”), suggesting that mc13 cells can be delivered systemically to the target tissue for rescue of dystrophin expression.

To test the pluripotent characteristics of mc13 cells in vivo, the cells were transduced with an adenoviral vector encoding rhBMP-2 (adBMP-2). The mc13 cells with adBMP-2 were then injected into hind limbs of SCID mice. The animals were sacrificed at 14 days post-injection, and the hind limbs were removed for histochemical and immunochemical analysis. Enzyme-linked immunosorbent assay (ELISA) analysis of mc13 cells transduced with adBMP-2 showed that infected cells were capable of producing rhBMP-2. Radiographic analysis of hind limbs of injected SCID mice revealed robust ectopic bone formation within 14 days of injection (FIG. 15E). Histological analysis using LacZ staining of the ectopic bone shows that LacZ positive mc13 cells were uniformly located within the mineralized matrix or lacunae, a typical location where osteoblasts and osteocytes are found (FIG. 15F).

To further confirm the role of mc13 in formation of the ectopic bone, the muscle sections were also stained for presence of dystrophin. As shown in FIG. 15G, the ectopic bone contained cells highly positive for dystrophin, suggesting that mc13 cells are intimately participating in bone formation. As a control, similar experiments were carried out with fibroblasts. Fibroblasts were found to support robust ectopic bone formation, but the injected cells were uniformly found outside of the bone, and none could be located within the mineralized matrix. This suggests that the fibroblasts are capable of delivering rhBMP-2 to form ectopic bone, but are unable to differentiate into osteoblasts. In this case, the cells participating in mineralization of the ectopic bone are most likely derived from the host tissue. Thus, these results demonstrate that mc13 cells can differentiate into osteoblasts, both in vivo and in vitro,

Enhancement of bone healing by genetically engineered muscle-derived cells: Skull defects (approximately 5 mm) were created in skeletally mature (6 8 weeks old) female SCID mice using a dental burr as described above. Previous experiments have demonstrated that 5 mm skull defects are “non-healing” (P. H. Krebsbach et al., 1998, Transplantation 66:1272 1278). The skull defect was filled with a collagen sponge matrix seeded with mc13 cells transduced or not transduced with adBMP-2. These mice were sacrificed at 14 days, and the healing of the skull defect was analyzed. As shown in FIG. 16A, the control group treated with mc13 cells without rhBMP-2 showed no evidence of healing of the defect. In contrast, the experimental group treated with mc13 cells transduced to express rhBMP-2 showed almost a full closure of the skull defect at 2 weeks (FIG. 16B). The von Kossa staining, which highlights mineralized bone, showed robust bone formation in the group treated with mc13 cells transduced to express rhBMP-2 (FIG. 16D), but minimal bone formation was observed in the control group (FIG. 16C).

The area of new bone in the experimental group was analyzed by fluorescence in situ hybridization (FISH) with a Y-chromosome specific probe to identify transplanted cells. As shown in FIG. 16E, Y-chromosome positive cells were identified within the newly formed bone, indicating active participation of transplanted cells in bone formation under the influence of rhBMP-2. The Y-chromosome negative cells were also identified within the newly formed skull, thus indicating active participation of host-derived cells as well. These results demonstrate that mc13 cells can mediate healing of a “non-healing” bone defect upon stimulation with rhBMP-2, and indicate that the MDCs of the present invention can be used in the treatment of bone defects, injuries, or traumas.

Example 10 Slowly-adhering Human MDCs are More Myogenic in Character and Improve Left Ventricular Function in Mice with Induced Myocardial Infarction

Populations of rapidly- and slowly-adhering MDCs were isolated from the rectus muscle of 3 male and 3 female donors (13 year old male, 57 year old male, 70 year old male, 32 year old female, 59 year old female, 64 year old female) obtained from the Center for Organ Recovery and Education (CORE). Biopsy size for 14 samples ranged from 42 to 247 mg. The average size was 129 mg. Rapidly- and slowly-adhering MDCs isolated from a 57 year old male donor were used for intracardiac injection.

Skeletal muscle biopsy tissue is immediately placed in cold hypothermic medium (HypoThermosol (BioLife) supplemented with gentamicin sulfate (100 ng/ml, Roche)) and stored at 4° C. After 3 to 7 days, biopsy tissue is removed from storage and production is initiated. Any connective or non-muscle tissue is dissected from the biopsy sample. The remaining muscle tissue that is used for isolation is weighed. The tissue is minced in Hank's Balanced Salt Solution (HBSS), transferred to a conical tube, and centrifuged (2,500×g, 5 minutes). The pellet is then resuspended in a Digestion Enzyme solution (Liberase Blendzyme 4 (0.4-1.0 U/mL, Roche)). 2 mL of Digestion Enzyme solution is used per 100 mg of biopsy tissue and is incubated for 30 minutes at 37° C. on a rotating plate. The sample is then centrifuged (2,500×g, 5 minutes). The pellet is resuspended in culture medium and passed through a 70 μm cell strainer. The culture media used for the procedures described in this Example was Cambrex Endothelial Growth Medium EGM-2 basal medium supplemented with the following components: i. 10% (v/v) fetal bovine serum, and ii. Cambrex EGM-2 SingleQuot Kit, which contains: Insulin Growth Factor-1 (IGF-1), Basic Fibroblast Growth Factor (bFGF), Vascular Endothelial Growth Factor (VEGF), Epidermal Growth Factor (EGF), Hydrocortisone, Heparin, and Ascorbic Acid. The filtered cell solution is then transferred to a T25 culture flask and incubated for 30-120 minutes at 37° C. in 5% CO₂. Cells that attach to this flask are the “rapidly-adhering cells”.

After incubation, the cell culture supernatant is removed from the T25 flask and placed into a 15 mL conical tube. The T25 culture flask is rinsed with 2 mL of warmed culture medium and transferred to the aforementioned 15 mL conical tube. The 15 mL conical tube is centrifuged (2,500×g, 5 minutes). The pellet is resuspended in culture medium and transferred to a new T25 culture flask. The flask is incubated for ˜2 days at 37° C. in 5% CO2 (cells that attach to this flask are the “slowly-adhering cells”). After incubation, the cell culture supernatant is aspirated and new culture medium is added to the flask. The flask is then returned to the incubator for expansion. Standard culture passaging is carried out from here on to maintain the cell confluency in the culture flask at less than 50%. Trypsin-EDTA (0.25%, Invitrogen) is used to detach the adherent cells from the flask during passage. Typical expansion of the “slowly-adhering cells” takes an average of 17 days (starting from the day production is initiated) to achieve an average total viable cell number of 37 million cells (n=14 production runs from 14 different biopsy samples with a biopsy weight range of 42-247 mg, average 129 mg).

Once the desired cell number is achieved, the cells are harvested from the flask using Trypsin-EDTA and centrifuged (2,500×g, 5 minutes). The pellet is resuspended in BSS-P solution (HBSS supplemented with human serum albumin (2% v/v, Sera Care Life)) and counted. The cell solution is then centrifuged again (2,500×g, 5 minutes), resuspended with Cryopreservation Medium (CryoStor (Biolife) supplemented with human serum albumin (2% v/v, Sera Care Life Sciences)) to the desired cell concentration, and packaged in the appropriate vial for cryogenic storage. The cryovial is placed into a freezing container and placed in the −80° C. freezer. Cells are administered by thawing the frozen cell suspension at room temperature with an equal volume of physiologic saline and injected directly (without additional manipulation). The lineage characterization of the slowly adhering cell populations (n=7 biopsies) shows: Myogenic (87.4% CD56+, 89.2% desmin+), Endothelial (0.0% CD31+), Hematopoietic (0.3% CD45+), and Fibroblast (6.8% CD90+/CD56−).

Following disassociation of the skeletal muscle biopsy tissue, two fractions of cells were collected based on their rapid or slow adhesion to the culture flasks. The cells were then expanded in culture with growth medium and then frozen in cryopreservation medium (3×10⁵ cells in 15 μl) in a 1.5 ml eppendorf tube. For the control group, 15 μl of cryopreservation medium alone was placed into the tube. These tubes were stored at −80° C. until injection. Immediately prior to injection, a tube was removed from storage, thawed at room temperature, and resuspended with 15 μl of 0.9% sodium chloride solution. The resulting 30 μl solution was then drawn into a 0.5 cc insulin syringe with a 30 gauge needle. The investigator performing the surgery and injection was blinded to the contents of the tubes.

Cell count and viability was measured using a Guava flow cytometer and Viacount assay kit (Guava). CD56 was measured by flow cytometry (Guava) using PE-conjugated anti-CD56 antibody (1:50, BD Pharmingen) and PE-conjugated isotype control monoclonal antibody (1:50, BD Pharmingen). Desmin was measured by flow cytometry (Guava) on paraformaldehyde-fixed cells (BD Pharmingen) using a monoclonal desmin antibody (1:100, Dako) and an isotype control monoclonal antibody (1:200, BD Pharmingen). Fluorescent labeling was performed using a Cy3-conjugated anti-mouse IgG antibody (1:250, Sigma). In between steps, the cells were washed with permeabilization buffer (BD Pharmingen). For creatine kinase (CK) assay, 1×10⁵ cells were plated per well into a 12 well plate in differentiation-inducing medium. Four to 6 days later, the cells were harvested by trypsinization and centrifuged into a pellet. The cell lysis supernatant was assayed for CK activity using the CK Liqui-UV kit (Stanbio).

The cells were injected into the hearts of NOD-SCID mice to avoid immune-rejection associated with xenotransplantation of human cells. The Institutional Animal Care and Use Committee, Children's Hospital of Pittsburgh, approved the animal and surgical procedures performed in this study (Protocol 37/04). Twenty-two weeks old, NOD.CB17 prkdc Severe Combined Immunodeficiency (NOD-SCID) mice (The Jackson Laboratory, Bar harbor, ME, USA) were used in this study. The mice were anesthetized with a gaseous mixture of isoflurane and oxygen and intubated. Positive-pressure ventilation was maintained with a ventilator during surgery. Acute myocardial infarction was induced by ligation of the left anterior descending coronary artery 2 mm from the tip of the normally positioned left auricle. Immediately after ligation, the prepared solution was injected into the anterior and lateral aspects of contracting wall bordering the infarct and into the center of the infarct (10 μl per region).

Two and 6 weeks after transplantation, echocardiography was performed to assess the left ventricular function. Echocardiography was performed by a blinded investigator using a Sequoia C256 system (Acusion, Mountain View, Calif., USA) equipped with a 13-Mhz linear-array transducer (15L8). Mice were anesthetized with isoflurane gas (3% isoflurane for 1 minute induction and 1.50% isoflurane for maintenance) and restrained in the supine position. Both end-systolic area (ESA) and end-diastolic area (EDA) were determined from short-axis images of the left ventricle. Fractional area change (FAC), an index of LV contractility, was calculated as FAC (%)=[(EDA-ESA)/EDA]×100.

Data is presented as mean±SE. Statistical differences in the cardiac function data was determined by a two-way ANOVA. Post-hoc analysis was performed with a Student-Newman-Keuls multiple comparison test.

Myogenic Characterization of Rapidly- and Slowly-adhering MDCs

In the cells isolated from the tissues of 6 different donors (3 male and 3 female), we observed that the populations of rapidly-adhering MDCs displayed lower levels of the myogenic marker CD56 expression (average of all 6 populations [avg.], 49.5%) when compared to the populations of slowly-adhering MDCs (avg. 71.0%) (FIG. 17). When the same number of cells for each group was subjected to conditions that induce myogenic differentiation, the rapidly-adhering MDCs (avg. 69 U/L) displayed lower creatine kinase activity levels than the slowly-adhering MDCs (avg. 142 U/L) (FIG. 17), indicating that the slowly-adhering cells are capable of producing larger quantities of muscle than the rapidly-adhering cells. Taken together, these results suggest that populations of slowly-adhering MDCs are more myogenic (CD56 content) and are more potent in terms of muscle generation (CK activity) when compared to populations of rapidly-adhering MDCs (FIG. 17).

Post-thaw Characterization of the Cells Packaged and Frozen for Injection

We analyzed post-thaw samples of the MDCs (isolated from a 57 year old male donor) that were packaged and frozen for intracardiac injection. Both cell populations had equally high percent viability (92%) immediately following thaw, indicating that a very high percentage of both populations of cells were viable at the time of injection (Table 1). The percentage of cells that expressed the myogenic marker CD56 was 43.8% and 85.1% for the rapidly- and slowly-adhering MDCs, respectively, as shown in Table 4.

TABLE 4 Characterization of the cells after thaw and resuspension Creatine Kinase % Activity viable CD56 % Desmin % (U/L) Rapidly- 92.0 43.8 62.5 82.0 adhering cells Slowly- 91.9 85.1 93.6 181.0 adhering cells (MDCs)

A similar trend was observed in the expression levels of the myogenic marker desmin for the rapidly- (62.5%) and slowly-adhering MDCs (93.6%). The myogenic potency of the cells as measured by CK activity after thaw was 82 and 181 U/L for the rapidly- and slowly-adhering cells, respectively. These differences in myogenic content (CD56 and desmin) and myogenic differentiation (CK) between these 2 populations indicate that the cells used for intracardiac injections are representative populations of rapidly- and slowly-adhering cells that are typically isolated from donor skeletal muscle (see FIG. 17).

Cardiac Function

MDCs that were isolated from the 57 year old male were used for intracardiac injections for 2 reasons. First, the rapidly- and slowly-adhering cell populations from this donor displayed myogenic characteristics that were representative of the cells isolated from the other donors as shown in Table 5 and FIG. 17.

TABLE 5 Functional improvement (percent increase from control). Rapidly-adhering Slowly-adhering cells cells (MDCs) 2 weeks 23.0 69.7 6 weeks 45.2 118.9

Second, the age and sex of the donor muscle biopsy seems to be compatible with the target population in need of such a therapy.

When compared to the control group, the hearts injected with either rapidly- or slowly-adhering cells displayed an improvement in LV contractility, as measured by FAC, as early as 2 weeks after myocardial infarction as shown in FIG. 18. Also, the results shown in Table 5 demonstrate 23.0% and 69.7% increases, respectively. By 6 weeks, LV contractility levels remained stable in either cell group but a modest decrease was observed in the control group, resulting in an even greater improvement in LV contractility for the hearts injected with rapidly-and slowly-adhering cells when compared to hearts injected with control medium 45.2% and 118.9%, respectively, as shown in Table 5 and FIG. 18. A significant difference in comparison to the control group was only achieved in the slowly-adhering MDCs group (FIG. 18; *P<0.05, slowly-adhering MDCs vs. control). In addition, the slowly-adhering MDC-injected hearts demonstrated superior LV contractility than did the hearts injected with rapidly-adhering cells (FIG. 18; † P<0.05, slowly-adhering cells (MDCs) vs. rapidly-adhering cells), suggesting that slowly-adhering MDCs are superior to rapidly-adhering cells for myocardial infarct repair.

We have isolated 2 fractions of cells based on their rapid or slow adhesion to the culture flask following disassociation of a human skeletal muscle tissue biopsy. The populations of cells that slowly adhered to the culture flask are characterized by a higher myogenic content and a greater myogenic efficiency/potency when compared to the populations of cells that rapidly attached. For myocardial infarct repair, hearts injected with either fraction of cells offered functional improvement when compared to hearts injected with control. However, the slowly-adhering cells provided superior functional recovery after myocardial infarction when compared to the rapidly-adhering cells.

All patent applications, patents, texts, and literature references cited in this specification are hereby incorporated herein by reference in their entirety to more fully describe the state of the art to which the present invention pertains.

As various changes can be made in the above methods and compositions without departing from the scope and spirit of the invention as described, it is intended that all subject matter contained in the above description, shown in the accompanying drawings, or defined in the appended claims be interpreted as illustrative, and not in a limiting sense. 

1. A method of improving left ventricular contractility in a mammalian subject in need thereof comprising; (a) isolating skeletal muscle cells from a human subject, (b) suspending the human skeletal muscle cells in a medium in a first cell culture container for between 30 and 120 minutes thereby producing a cell population of adherent cells and a population of non-adherent cells; (c) decanting the medium and the population of non-adherent cells from the first cell culture container to a second cell culture container; (d) allowing the population of the decanted non-adherent cells in the medium from the first cell culture container to attach to the walls of the second cell culture container for 1-3 days; (e) isolating the population of cells adhered from the walls of the second cell culture container, wherein the isolated population of cells are muscle-derived progenitor cells (MDCs); and (f) administering the MDCs to the heart of the mammalian subject; thereby, improving left ventricular contractility of the heart.
 2. The method of claim 1, wherein the MDCs are administered by injecting them into the heart.
 3. The method of claim 2, wherein the MDCs are injected into the heart wall.
 4. The method of claim 1, wherein the mammal is a human.
 5. The method of claim 1, wherein the MDCs are cultured to expand their number before administering to the heart of the mammalian subject.
 6. The method of claim 1, wherein the MDCs are frozen after said isolating step of (e) and thawed prior to said administering step of (f).
 7. A method of isolating an end population of mammalian skeletal muscle-derived progenitor cells (MDCs) comprising (a) suspending human skeletal muscle cells in a medium in a first cell culture container for between 30 and 120 minutes thereby producing a cell population of adherent cells and a population of non-adherent cells; (b) decanting the medium and the population of non-adherent cells from the first cell culture container to a second cell culture container; (c) allowing the population of the decanted non-adherent cells in the medium from the first cell culture container to attach to the walls of the second cell culture container for 1-3 days; and (d) isolating the population of cells adhered from the walls of the second cell culture container, thereby, isolating said end population of MDCs.
 8. The method of claim 7, wherein the MDCs are subsequently frozen.
 9. The method of claim 8, wherein the MDCs are frozen at a temperature below −30° C.
 10. The method of claim 8, wherein the MDCs are frozen at a temperature below −70° C.
 11. The method of claim 8, wherein the MDCs are frozen on dry ice. 